Category: Biology

Acclimatization: Introduction

An organism’s capacity to adapt to changes in its environment is crucial to its ability to survive. An organism adapts to its changing environment by either acclimating to it or by adapting to it. Acclimatization occurs quickly and results in temporary physiological changes that guarantee survival. In contrast, adaptation leads to the creation of new characters over time, ensuring the survival of the organism.

In species exposed to novel environmental factors such pH, salinity, light, pressure, chemicals, altitude, and temperature, a physiological process called acclimatisation occurs naturally. Acclimatization results in certain  modifications that  enable the organisms to endure a wide variety of contrasting environmental circumstances.

Acclimatization in Human

Similar to other organisms, the human body adapts to abrupt changes in the environment. This facilitated the long-term survival of the human race and the expansion of the species to areas of the world with diverse climatic conditions. As an illustration, when a person relocates to a very hot region, his body begins to reduce the amount of salt he loses through perspiration, although perspiration increases to keep him cool. In addition, our body’s capacity to acclimate is what allows us to climb tall mountains and descend deep into the ocean. Let’s go deeper into the high altitude adaptation process.

Acclimatization at Higher Altitudes

Higher altitude regions are those that are positioned above 2,400 meters above sea level. Compared to locations close to sea level, these areas have a cooler climate. With rising height, the air pressure falls. Additionally, there is less oxygen in the atmosphere. High-altitude regions include, for example, the Himalayan mountain ranges.

Mechanism of acclimatization to higher altitudes

• When exposed to shifting climatic circumstances at higher altitudes, humans can experience changes in their personalities as well as cognitive abilities. 
• The carotid bodies respond to low oxygen levels in the air that are inhaled.
• The rate and depth of breathing are increased by these arterial chemoreceptors.
• Erythropoietin is released by the kidneys in response to decreased oxygen pressure in the arteries. This encourages the bone marrow to produce red blood cells.
• People exposed to an increase in altitude experience a variety of alterations, including changes in the composition of oxidative enzymes, a reduction in the distance between capillaries, and changes in the affinity of hemoglobin towards oxygen.

Consequences to exposure to higher altitudes

• The stroke volume decreases as a result of a higher heart rate, which also reduces non-essential physiological activities like digesting.
• Respiratory alkalosis, a decrease in lactate synthesis, and an increase in 2,3-bisphosphoglycerate are a few prominent chemical alterations in the body.
•  In pregnant women, such environmental conditions can restrict intrauterine growth, reduce placental blood flow, and thereby reduce the height of such children born.
• Mountain sickness, oedema in the lungs and brain, weight gain from fluid retention, increased ventilation, sleeplessness, vomiting, dizziness, and weariness are other symptoms of high altitude.
• If people rise at a faster rate, the high altitude effects mentioned above take place. The body becomes momentarily accustomed to the changing environment if the necessary amount of time is given for it to do so.

Oxygen level at higher altitudes 

• Since oxygen is almost insoluble in water, it is mostly carried by the hemoglobin present in erythrocytes (RBCs) instead of blood plasma. 
• A maximum of four oxygen molecules can attach to one hemoglobin molecule to generate oxyhemoglobin. This reaction is reversible. 
• The partial pressure of oxygen directly affects how much oxygen binds to hemoglobin. 
• With the increase in altitudes the partial pressure of oxygen decreases. As a result less oxygen is available for use.
• Thus, hemoglobin releases more bounded oxygen to the tissues. It can so happen that all the bounded oxygen is released.
• Since the O2 pressure at higher altitudes is low, more hemoglobin is also produced by the body. This is done so that the maximum amount of oxygen can be absorbed available in the atmosphere. 
• This is the reason why people living in high-altitude regions have significantly  red-colored cheeks as compared to people living at the sea-level.

Oxygen-dissociation Curves

• A typical oxygen dissociation curve demonstrates that hemoglobin initially binds to oxygen with difficulty, and that difficulty decreases with subsequent bindings—for example, the first oxygen molecule to deoxyhemoglobin is harder to bind to, than the second one which is comparatively easier to bind, the third one is even more easier to bind to, and so on.
• The oxygen molecules’ ability to bind to hemoglobin is influenced by a number of parameters.
• Temperature, pH, carbon dioxide, carbon monoxide, and 2,3-BPG all affect  the binding of oxygen to hemoglobin.

Difference between Acclimatization and Adaptation

Myoglobin

• Specialized molecules that bind to oxygen are found in skeletal muscles.These molecules are known as
• Myoglobin which is single polypeptide chains.
• Since they are made up of a single heme molecule, they can attach to one oxygen molecule at a time.
• The graph of it displays a logarithmic pattern as opposed to the sigmoidal curve  of hemoglobin molecules .
• When engaged in vigorous activity, myoglobin exhibits a delayed release and a strong affinity for oxygen.

Summary

The process through which an organism adapts to changes in its environment, including those related to temperature, altitude, humidity, pH, light, salinity, pressure, etc is termed  acclimatization. It is a reversible process. It is a physical change and does not change the genetic composition of an organism. One example of acclimatization in humans is seen when humans travel to a higher altitude. At higher altitudes, oxygen levels and the temperature are low. Thus various internal changes such as increased hemoglobin production, increased rate, and depth  of breathing, changes in the affinity of hahemoglobinowards oxygen, etc are observed. These changes are observed as a response to the change in the environment. It is the body’s way to acclimatize to new environmental conditions.

Frequently Asked Questions

1. How oxygen dissociation curve of a foetus is different from an adult?

Fetal hemoglobin has a slightly different composition than adult hemoglobin, which results in an increase in its affinity for oxygen molecules. In the placenta, where maternal hemoglobin is unloaded, it can load oxygen. The replacement of fetal hemoglobin with adult hemoglobin takes roughly six months after delivery.

2. Under which conditions does the oxygen dissociation curve move towards the right?

A shift towards the right side of the graph is seen under the following conditions-

• The oxygen partial pressure falls.
• Carbon dioxide’s partial pressure rises.
• Concentration of hydrogen ions rises.
• Decreases in pH or acidity.
• A rise in body temperature.
• An excess of 2,3-Diphosphoglycerateb is formed which is a byproduct of glycolysis.

3. What are the three stages of high altitude acclimatization?

The 3 stages of  high altitude acclimatization are-

• Preparation stage- In this stage the person is prepared for the going to a higher altitude. He/She is given proper training and is exposed to the cold temperatures and low oxygen environment.
• Ascent stage- This is the stage when people begin to move up the altitude, i.e .they climib the mountain.
•  Descent stage– This is the stage when people begin to come down.i.e they start climbing down the altitude and start coming to a region where temperature is high and oxygen-levels are also normal.

Introduction

Plants can reproduce sexually or asexually in nature. The fusing of male and female sex cells, or gametes, is the primary mechanism for sexual reproduction in plants, as it is in all other species.Through the use of specialised structures such modified stems and roots, plants are capable of reproducing asexually. Human action, such as cutting off a plant’s parts and giving the cuttings favourable conditions to encourage the formation of roots, can also lead to asexual reproduction in plants .

Asexual Reproduction

In its most basic form, asexual reproduction  in which the organism is simply divided into two and only single parent is involeved. This type of reproduction is  without the formation of gametes. Here a single parent-cell divides, giving rise two daughter cells. The progenies thus born are genetically and physically identical to the parent cell. Single-celled organisms frequently employ this technique for reproduction

There are two ways:

Natural Asexual Reproduction

Under natural vegetative propagation, plants reproduce through natural asexual processes, which do not require human involvement. Following are natural ways of asexual reproduction in plants-

• Vegetative propagation:

Plants reproduce in this type of asexual manner without making seeds or spores. The plant instead relies on a few special parts that,under appropriate conditions, grow into new plants.These  plant elements are-

• Rhizomes:Rhizomes are modified stems that can produce new plants by generating advententious roots and shoot systems at their nodes. Examples include bamboo and ginger.

• Stolons: Stems that extend horizontally from the ground are called runners or stolons. New roots form at the nodes as they spread,thus eventually producing a new plant. Examples include strawberries, mint, etc.
• Tubers: Known as stem tubers and root tubers, respectively, these are swollen stems or roots. The buds that are present on the surfaces of these modified parts can store enough nutrients to sustain the formation of a new plant. Potato and sweet potato are two examples.
• Leaves: Some plants, such as Kalanchoe and Begonia, have plantlets on the margins of their leaves. These plantlets eventually grow roots and branches to form new plant systems.
• Apomixis:

Asexual reproduction of flowering plants using seeds is called apomixis, also referred to as agamospermy.  Following types of apomixis are:

• Nonrecurrent apomixis: In this sort of apomixis, the gametophyte or another haploid egg cell (haploid parthenogenesis) is used to form the embryo

• Recurrent apomixis: In this case, without fertilisation, the embryo sac develops from the diploid archesporium or a non-archesporial diploid cell of the gametophyte.
• Nucellar embryony: The embryo develops from cells of the integuments or diploid nucellar tissue. The resulting embryo is therefore also diploid.

Artificial Asexual Reproduction

Artificial asexual reproduction occurs under human intervention. Techniques like cutting, grafting, layering and tissue culture are considered types of artificial asexual reproduction.

• Cutting: In this method of propagation plant parts like the stem and leaves are cut and placed in the ground.These cut-off portions eventually develop into adventitious roots (from shoot cuttings) or adventitious shoots (from roots cuttings).When using leaf cuttings, adventitious roots and shoots can form. To promote the quick development of new roots in the cuttings, rooting hormones are frequently employed.
• Grafting:Grafting is removing the stem or other aerial parts of a plant and attaching them to the shoot of an another plant. The plant into which it is attached is known as the stock, and the cut-off portion is known as the scion. The cambial tissues of the two plants will eventually combine and develop into a single unit. For dicot plants that are botanically related, this method shows to be particularly effective. Bud or shoot grafting are two types of grafting.
• Layering: Layering is the act of bending a branch or stem and putting int into th soil, while it is still connected to its parent plant.The newly planted branch quickly forms adventitious roots and becomes a new plant.

Advantages of Asexual Reproduction

• The faster rate of offspring development is one of the most obvious benefits of asexual reproduction.
• Without being restricted to circumstances like gamete creation, gamete fusion, or seed generation, asexual reproduction techniques—whether natural or artificial—produce great outcomes, giving rise to a healthy plant under favourable conditions.
• Asexual reproduction permits limitless generation of genetically identical offspring. As a result, it is possible to grow a lot of young plants from a parent plant that possesses desired traits.
• Employing such plants that can develop by asexual ways of reproduction proves to be inexpensive, especially when cultivating plants on a commercial scale.
• The advantages provided by asexual propagation in the commercial production of plants include shorter times, no need for seeds, a favourable environment for pollination, seed dispersals, etc.

Disadvantages of Asexual Reproduction:

• Lack of genetic variety in the progeny and parent plants is one of the most important drawbacks of asexual reproduction.
• Due to this the spread of hereditary illnesses and undesirable traits will also increase.
• Furthermore, not all individuals are capable of carrying out artificial asexual reproduction procedures.

Summary

• Plants can reproduce asexually without the development of gametes or gamete fusion.
• Plants can reproduce asexually spontaneously or through human intervention.
• Various components, including tubers, bulbs, rhizomes, stolons, and plantlets, are used in natural asexual reproduction.
• Another form of asexual reproduction that utilises seeds is apomixis. Recurrent apomixis, non-recurrent apomixis, and nucellar embryony are different types of apomixis.
• Techniques like cutting, grafting, layering, and tissue culture are included under artificial asexual repoduction.
• Plants can reproduce asexually, which has benefits such not requiring seed formation and costing less time and money.
• The lack of genetic variation in the plants is the biggest drawback of asexual propagation.
  
  You can also read our blog about asexual reproduction for more details.

Frequently Asked Questions

1.What is Plant Tissue Culturing?
Ans: This method entails the in vitro propagation of a chosen genotype by cultivating plant cells, tissues, or organs like roots, shoot tips, and leaves, in a synthetic nutritional medium, under precise chemical and physical conditions.Examples of plant tissue culture include callus, cell, protoplast, meristem, embryo and organ cultures. The plants obtained from this technique are called microplants.

2.What are bulbs and how they help in asexual reproduction?
Ans: Blubs are modified stems with concentrically organized fleshy leaves. These bulbs include a new shoot system that develops into an entire new plant. This new shoot system reveives its nutrietion from the surrounding by fleshy, scaly leaves. Onions, garlic, and shallots are a few of the well-known examples of plants that reproduce by developing new bulbs.

3.Enlist 3 hormones used in artificial propagation of plants.
Ans: The hormones used in artificial propagation of plants are-

• Auxin- Helps in root formation.
• Gibberllin- Increases height of plant.
• Cytokinins- Helps in shoot formation.

Introduction

Different metabolic processes are carried out by organisms in order to ensure their existence and to produce progeny. Naturally occurring macromolecules i.e. nucleic acids hold genetic information.RNA and DNA are both types of nucleic acids. These are nucleotide-based macromolecules. DNA is the genetic substance that contains the genetic instructions for unique traits that are expressed as various characters by organisms.

Some viruses have RNA as their genetic material. Almost all cells contain RNA, which plays a specific role in protein synthesis.

DNA

• Deoxyribonucleic acid, usually referred to as DNA, is the genetic substance found in many organisms.
• It is a simple, tightly wound circle in the cytoplasm of prokaryotes.
• In the cell nucleus of eukaryotes DNA is tightly wound into chromosomes.
• Despite being long polymers, nucleic acids are tightly wrapped to fit inside the small cell.
• Even in massive multicellular animals, every cell in the body contains the same copy of DNA.
• During replication, the tightly wound structures are unwrapped to create copies.
• Eukaryotes also have mitochondrial DNA, which codes for proteins exclusive to mitochondria, in addition to the nucleus.

 Composition

• The nucleic acids are long polymeric chains of individual nucleotides.
• The phosphate group, pentose sugar moiety, and a nitrogenous base are all components of nucleotides.
• There are 4 types of nitrogenous bases found in DNA; adenine and guanine are purines while thymine and cytosine are pyrimidines.
• Deoxyribonucleic acid, or DNA, is made up of long chains of individual deoxyribonucleotides connected by phosphodiester linkages.
• The arrangement of nitrogenous bases corresponds to the arrangement of long chains of nucleotides in a  DNA, this sequence encodes the information on DNA and is original to an organism.

Structure

• DNA forms a right-handed double helix with an antiparallel orientation of the two polynucleotide strands. DNA structure resembles a twisted ladder shape.
• The sugar and phosphate groups make the vertical stands of the twisted ladder shape and nitrogenous base pairs resemble the rungs of a ladder. 
• The 3′ carbon of one sugar and the phosphate group linked to the 5′ carbon of the subsequent sugar moiety form a phosphodiester linkage.
• Because of this, the connection is sometimes known as a 3′–5′ phosphodiester linkage.
• A glycosidic bond attaches nitrogenous bases to the first carbon of the sugar.
• Through hydrogen bonding, the nitrogenous bases of opposing strands bind with each other.
• Three hydrogen bonds link cytosine and guanine, while two hydrogen bonds pair adenine and thymine. This is known as complementary base paring.
• The double-helical DNA is twisted with 10 base pairs per turn.
• The deep major grooves and shallow minor grooves are created by these helical turns.

Types of DNA 

 There are two types of DNA depending on where they are located in the cell. The two types of DNA are-Nuclear DNA and Mitochondrial DNA 

• Nuclear DNA- Exists as chromosomes in the nucleus. It is huge and is in response of nearly all the characteristics of an organism.
• Mitochondrial DNA- DNA found in mitochondria is known as mitochondrial DNA. This DNA  primarily codes for proteins needed for the mitochondrial activity. It originates from the female parent and manifests in the mitochondrial matrix as small circular shapes.

RNA

• RNA is also known as Ribonucleic acid.
• Phosphate group, pentose sugar moiety (ribose), and nitrogenous base are all components of ribonucleotides.
• The ribonucleotides include adenine, guanine, cytosine or uracil.
• RNA can be found as single or double-stranded.
• Nearly every cell has RNA, which serves an important role in protein synthesis.
• RNA serves as the genetic material in several viruses.

Types of RNA 

There are three types of RNA found. They are

mRNA or messenger RNA

• mRNA is formed from DNA through transcription. The base pairs of m-RNA are complimentary to base sequences on DNA.
• The nucleotide sequences of mRNA are organized into triplets called codons.
• While several codons can code a single amino acid, each amino acid has a unique codon.
• 64 codons encode twenty amino acids.
• Pre mRNA, a direct byproduct of transcription, undergoes post-transcriptional modifications to become mRNA.
• A guanine group and poly-A tail are added to the pre-mRNA during post-transcriptional modifications to make it more stable.
• The mRNA is the main precursor of protein synthesis.
• It delivers the genetic information from the DNA for protein synthesis. 

rRNA or ribosomal RNA

• They are found in ribosomal subunits along with proteins and enzymes.
• The primary component of ribosomes is ribosomal RNA (rRNA).
• It enables the formation of peptide bonds between two amino acids during protein synthesis. 
• It also ensures that the mRNA and ribosomes are properly aligned during protein synthesis.

tRNA or transfer RNA

• tRNA is important for protein synthesis.
• During translation, amino acids are transferred by the tRNA.
• Each amino acid has a unique tRNA that transports it to the translation site (ribosome).
• It is the smallest of all RNA.
• tRNA has a structure resembling a clover leaf.

Role in protein synthesis  

• Translation is also known as protein synthesis and it  occurs in the ribosomes.
• Proteins are long polypeptide chains that are formed when individual amino acids bind to one another through peptide bonds.
• Each of the three RNA types plays a distinct role in translation-
• Single-stranded mRNA contains the instructions needed to make proteins.
• tRNA interprets the genetic code on the mRNA and the specific amino acids are transported from the amino acid pool to the translation site.
• The ribosomal RNA (rRNA) carries out translation by creating peptide bonds between different amino acids.

Difference between DNA and RNA

DNA	RNA
DNA is Deoxyribonucleic Acid	RNA is ribonucleic acid
It is made up of Adenine, guanine, cytosine, and thymine	It is made up of Adenine, guanine, cytosine, and uracil
Very stable structure	Comparatively less stable structure
Less prone to mutations	More easily prone to mutations
Present in Nucleus and mitochondria.	Present in the Cytoplasm, ribosomes, and nucleus
It is Self-replicating.	Most of the RNA is dependent on DNA for its synthesis.
It is the genetic material of most organisms and helps in the transfer of information from one generation to another.	It is most essential component during protein synthesis.
3 forms of DNA are B-DNA, A-DNA and Z-DNA.	3 types of RNA are found: m-RNA, r-RNA and t-RNA.
Contains a Deoxyribose sugar	Contains a ribose sugar

Summary

The nucleic acids in living things are DNA and RNA. They are organic polymers that are found in nature.  Long chains are created by linking the individual nucleotides together with phosphodiester linkages. In the majority of species, DNA, which is found in the nucleus of the eukaryotes, is the genetic information carrier. In order for the long polymeric chains to fit into the smallest microscopic cells, they must be folded numerous times. RNA primarily functions in protein synthesis. The existence of nucleic acids results in the continuation of life and the performance of particular tasks.

Frequently Asked Questions

1. Difference between 3 forms of DNA.
Ans:

B-DNA	A-DNA	Z-DNA
92% relative humidity	75% relative humidity	High and low salt concentrations
10bp	11bp	12bp
Right-handed	Right-handed	Left-handed
Widest of all	Width 2nm	Narrowest
Most common and stable form	Metastable form	Unstable and has Zig-zag pattern of phosphodiester backbone.

2. What is central dogma?
Ans: The central dogma is a theory of molecular biology that states that genetic information can only move in a single direction i.e  from DNA to RNA to protein. This protein synthesis takes place via three process-

• Replication- This multiplies the DNA stands.
• Transcription–This makes mRNA which encodes information of the DNA.
• Translation- This makes the final proteins that perform various functions in the body.

3.What is a chromosomes?
Ans: The DNA molecule is packed into chromosomes, which are thread-like structures found in the nucleus of every cell. Each chromosome is constructed from DNA that has been tightly wound around proteins called histones which assists in supporting entire chromosome structure.

Introduction

Through the process of reproduction, an organism gives rise to offspring that are biologically related to the organism.

Reproduction enables and ensures species continuity generation after generation.

There are essentially two types of reproduction:

• Sexual reproduction
• Asexual reproduction

Asexual reproduction

The simplest type of reproduction is asexual reproduction, which doesn’t involve gamete creation, meiosis, or fertilization. These types of reproduction only need one parent, and the resulting individuals, or clones, are genetically identical. Asexual reproduction is also referred to as clonal propagation. Animals can reproduce asexually through a variety of mechanisms, including Binary Fusion, Fragmentation, Budding, Parthenogenesis, Gemmules, Regeneration, etc.

Features of asexual reproduction

• A single parent is involved.
• Neither fertilization nor gamete formation takes place.
• This reproduction process happens in a relatively short amount of time.
• The organisms multiply and grow swiftly.
• The offsprings are similar genetically.

Types of asexual reproduction

• Binary Fission

• • Bacteria and amoebas are the two main species that utilize this method of reproduction.
  • This occurs when the DNA of the parent bacteria breaks into two fragments, each of which has its DNA.
  • As a result, the parent cell splits into two identical daughter cells.

• Fragmentation:

• • In this method of asexual reproduction, the parent organism is divided into multiple fragments, each of which develops into a new organism.
  • This method of reproduction is mostly seen in starfish. For instance, the arm can give birth to an entirely new organism.

• Gemmules:
• • • In this kind, the parents release a highly developed mass of cells, which eventually give rise to offspring.
    • The development of these gemmules occurs when parents face unfavorable environmental conditions.

• Parthenogenesis: 

• • In this type of asexual reproduction, the female organism produces eggs without fertilization, These eggs give birth to offspring.
  • Examples are lizards, certain fish, and insects.
• Regeneration:
• • Regeneration is the replacement of a missing part or the growth of an organism’s entire body from a small portion (morphallaxis) (epimorphosis).
  • It is primarily found in planaria, sponges, amoebas, and many other organisms.
  • There are 2 types of regeneration-
  • Reparative regeneration: Only some kinds of damaged tissues are capable of regeneration.
  • Restorative regeneration: In this, severed body parts can be restored or grown into a complete body.

• Budding:

• • In this type of reproduction, the child grows on the parent’s body much like a bud. Echinodermata and Hydra are two well-known examples of this type of asexual reproduction.
  • Here, the bud begins to live independently after separating from the parent plant.
  • There are two types of bidding-
  • Exogenous or External budding: A bud forms on the exterior of the body in this sort of budding. This growing bud learns to live alone after becoming separated from its parent. Newly formed buds have two choices: they can remain attached to their parents or they can detach and create their offspring.
  • Endogenous or internal budding: In a few marine sponges, buds form inside the bodies of the sponge parents (e.g. Spongilla).

Advantages of asexual reproduction

• An organism can give birth to a large number of offspring, swiftly increasing that species’ population.
• There is no need for another parent organism since asexual reproduction involves only one parent.
• Animals can reproduce asexually without their gametes fusing, thus gamete formation is not required.
• Because mating is not required, less energy is used.
• Sexual reproduction is outpaced by the offspring’s rate of asexual reproduction.

Disadvantages of asexual reproduction

• Population growth is accelerating due to asexual reproduction, therefore difficult to control the population of only one species.
• They compete with one another since both species rely on the same habitat for survival.
• The atmosphere must be conducive for both the parent and the offspring.
• Children are biologically identical to the single-parent organism.
• Genetic variety does not exist in this type of reproduction.

Summary

In conclusion, asexual reproduction is a sort of reproduction in which an offspring is born from a single parent. Since the newly reproduced organisms are physically and genetically similar, they are genetic clones of their parents. Asexual reproduction is present in multicellular and unicellular animals. During this reproduction,  gamete fusion does not take place. There are various types of asexual reproduction- such as fragmentation, binary fission, regeneration, etc.

Frequently Asked Questions

1. Different types of binary fission.
Ans: There are 4 types of binary fission-

• Simple binary fission: This fission can occur through any organism’s plane. Eg- Amoeba.
• Longitude binary fission: It is also referred to as longitudinal binary fission since it takes place along the longitudinal plane. Longitude binary fission is a process that occurs in flagellates like Euglena.
• Transverse binary fission: The cell division takes through the transverse plane. Prominent examples of this binary fission include Paramecium, Planaria, Diatoms, and bacteria.

• Oblique binary fission: In this process, the cytoplasm divides obliquely. Oblique binary fission takes place with cerium.

2. What does Hermaphrodite mean?
Ans: Hermaphrodite or bisexual animals are those that have both male and female reproductive systems. Earthworms and snails are a couple of examples.

3. What is strobilation?
Ans: Strobilation is the practice of repeatedly forming similar segments through the budding process. A strobila (also known as a scyphistoma) larva is a segmented portion of the body, while an ephyra larva is a segmented larva (a coelenterate).

Introduction

More than 70% of the surface of the world is made up of water bodies. These water bodies are known to harbor a complex ecosystem of different creatures that interact with one another and the surrounding water body. An ecosystem that is contained within water is known as an aquatic ecosystem. Both biotic and abiotic components make up these ecosystems. Numerous different types of species, including microbes, plants, invertebrates, fish, etc., are supported by these ecosystems.

Types of Aquatic Ecosystems

Aquatic ecosystems are of two types depending on the salinity of the water.  Two types of Aquatic ecosystems are-

• Freshwater ecosystems: 

• • These ecosystems, which make up only roughly 2% of the earth’s surface. They have a salt concentration of less than 0.1%. Rivers, streams, lakes, etc. are included in this type of ecosystem.

• Marine ecosystems: Marine waterbodies occupy up to 75% of the earth’s surface. These habitats have a salt concentration of 3% and are the most common type of aquatic ecosystem found throughout the globe. The marine ecosystems consist of oceans, seas, and estuaries.

Features of Aquatic Ecosystem

• Zonation in aquatic biomes

• • Aquatic systems frequently exhibit both vertical and horizontal stratifications of both physical and chemical components.
  • The types of biodiversity and dominance of organisms in an ecosystem are determined by these zones.

• Lakes and oceans can be classified into photic and non-photic zones based on the penetration of light:
  • Photic zones are those parts of the surface and subsurface where light- penetration is high. These regions are well-lit and show great biodiversity. The epipelagic zone comes under this category.
  • Aphotic zones are darker regions. Due to higher depth and decreased sunshine penetration, the aphotic zones are dark areas and they include bathypelagic and abyssopelagic zones.
• The lakes are classified into the littoral zone and the limnetic zone based on their distance from the beaches.

• • Since it is closest to the shore, the littoral zone has strong sunlight penetration.Due to this rooted aquatic plant growth is seen and it  also supports a large number of species.
  • The off-shore, open water area of an aquatic body is known as the limnetic zone. In contrast to the littoral zone, light only reaches the surface and subsurface regions.

• The ocean is further classified into three zones: the oceanic zone, the neritic zone, and the intertidal zone depending on the distance from the shore.

 

• Lifeforms

• Based on their position in the food chain, the lifeforms in aquatic ecosystems can be classified as producers (phytoplankton and plants), consumers (zooplankton, invertebrates, and fish), and decomposers (microorganisms).
• Based on their habitat within the environment, they can also be classified as periphyton, plankton, neuston, nekton, and benthic.
• The littoral zone is where rooted and floating plants can be found in freshwater habitats.
• Planktons, bacteria, fish, and other aquatic lifeforms predominate in the limnetic zone whereas invertebrates live in the benthic zone.
• Worms, clams, crabs, echinoderms, and other organisms can be found in the ocean’s intertidal zones, whereas phytoplankton and zooplanktons, as well as krill, jellyfish, fish, squids, turtles, and mammals, can be found in the ocean’s pelagic zones.

 

• Thermal stratification 

According to changes in temperature, aquatic habitats frequently have layers. Thermal stratification refers to this change in temperature with depth in an aquatic body.  During summer, the upper layer of water becomes significantly warm and less dense, while the lower layers remain cooler, leading to stratification.Epilimnion, Metalimnion,  and Hypolimnion are the names of the several strata.

• Seasonal changes in water temperature (Lake turnover)

As a result of shifting temperature profiles, many lakes experience seasonal mixing of their water, which results in a cyclical pattern.

During the spring and fall, this turnover allows oxygen-rich water to reach the lake’s bottom areas while also bringing nutrient-rich water to the surface.

• Available nutrients

Freshwater habitats can be classified as oligotrophic, mesotrophic, or eutrophic lakes depending on the amount of nutrients that are available to them. Oligotrophic lakes have more nutrients,  mesotrophic lakes have comparatively fewer nutrients and eutrophic lakes hthe ave least nutrients.

• Dissolved Oxygen(DO)

The water’s temperature affects the oxygen saturation levels. The higher the oxygen levels, the lower the temperature. Fish and other aquatic life are threatened by low amounts of dissolved oxygen. DO determines the richness of aquatic habitat.

Functions of Aquatic Ecosystem

• The aquatic ecosystem is a vital resource that sustains a wide range of creatures, including mammals, invertebrates, and microbes like bacteria and algae.
• An essential connection between the hydrosphere, lithosphere, and atmosphere is provided by the water bodies.
• A significant amount of the planet’s rainfall is caused by water evaporating from the oceans.
• Photosynthesis is carried out by marine photosynthetic bacteria and algae.
• 50 percent of the annual photosynthesis is produced by the ocean.
• Climate change and regional and planetary wind patterns are known to be influenced by oceans and their winds.
• The microbial decomposers that break down organic materials include bacteria and some types of fungi.
• The microorganisms that live in aquatic ecosystems ensure that nutrients are continuously cycled.
• The aquatic systems’ inhabitants, such as fish and other invertebrates, provide food and boost the economy.
• These aquatic ecosystems serve as water purification systems naturally.
• They aid in controlling floods and pollution
• Aquatic environments are used for recreation and transportation.

Summary 

• An aquatic ecosystem comprises any ecosystem supported by a water body.
• Aquatic environments can be either freshwater or marine, depending on salinity.
• Depending on criteria like sunlight penetration, distance from the shore, depth, etc., aquatic habitats are classified into several zones.
• Additionally, each layer’s biodiversity is determined by zonation.
• There is thermal stratification in aquatic habitats.
• Benthic, neuston, nekton, and planktonic creatures are all supported by aquatic ecosystems.
• Aquatic ecosystems perform a wide range of tasks, such as promoting biodiversity, nutrient cycling, flood attenuation, influencing global climate change, etc.

Frequently Asked Questions

1. What are the types of freshwater ecosystems?
   Ans: There are two types of freshwater ecosystems, they are-

• The lotic ecosystem: Moving waterbodies, such as springs, rivers, and canals, are included in this type of freshwater ecosystem.
• The lentic system: This type of freshwater ecosystem includes stagnant water bodies such as ponds and lakes. These water bodies are home to a variety of organisms.

2. Describe the Pelagic zone and Benthic zones
   Ans: Pelagic zone- The pelagic zone is the off-shore, open-water region of an aquatic ecosystem. Phytoplankton, zooplankton, and nekton live there. Zooplankton is the main consumers of the oceans and lakes, while phytoplankton makes up the photosynthetic producers. The most common producers here are algae.
   Benthic zone-The lowest biological zone is the benthic zone. The organisms that reside on the bottom of lakes or oceans are called Benthos. These benthic animals and microbes gather food that sediments down from the photic layers, ie., they are filter feeders.

3. What is a neritic zone?
   Ans: The area of the ocean that is relatively shallow, measuring around 200 metres (660 feet) deep, is known as the neritic zone (or sublittoral zone). Physical oceanography sees it as the location where the oceanic system interacts with the coast, whereas according to marine biology it is a part of the ocean, which forms a stable and illuminated environment for marine life, from plankton up to giant fish and corals to grow and survive.

Introduction

Transport is a crucial component of plant physiology and involves moving organic nutrients and water throughout the plant body. Food is produced by photosynthesis in the leaves which is transported to other parts of the plant and water is absorbed from the soil through the roots and then to various aerial regions of the plant. In higher plants, the transport of food and water takes place through specialized structures known as the xylem and phloem. An elaborate root system helps these plants to absorb water from the soil.  However, primitive plants perform the function of absorption of water through simple structures such as pores, or the external body surface.

For more help, you can Refer to our video in Class 7 Science in Lesson no 11. Check out the video Lesson for a better understanding.

Transportation in plants-

The main 3 means of transport in plants are via diffusion, Facilitated diffusion, and Active transport. Vascular bundles assist in the movement of water and carbohydrates throughout the entire plant body.

Simple Diffusion- Diffusion is the process of movement of a molecule from a location of higher concentration to a lower concentration i.e. along the concentration gradient. It is a spontaneous process and doesn’t require any energy. Here no special membrane proteins are required and this method only allows the transportation of hydrophobic molecules as the cell membrane is made up of a lipid bilayer.

• Facilitated diffusion- Facilitated diffusion is a type of diffusion facilitated by some proteins which assist in the movement of various metabolites through the cell membranes. These are majorly used for the transportation of water, ions, and other hydrophilic molecules which cannot pass through the lipid bilayer. The channel proteins and the carrier proteins are the two different types of membrane transport proteins.
• Channel proteins- Pores in the plasma membrane are created by channel proteins. These proteins are highly selective and hence allow the transportation of specific molecules only. Eg-Aquaporins only permit water movement and Aquaglyceroporins facilitate only the movement of glycerol and water.
•  
• Carrier proteins- These are special types of proteins that undergo conformational changes after binding to a particular solute. Carrier proteins help in the transportation of ions eg- chloride-bicarbonate exchanger, also known as the anion exchange protein, which facilitates the simultaneous transit of HCO3- and Cl–. It also helps in the transport of glucose via the glucose transporter(GLUT).
• Active transport- Active transport facilitates uphill solute movement throughout the cell by functioning against a concentration gradient. Here the molecules move from an area of lower concentration to a higher concentration. Hence, some kind of energy is required. There are two ways to supply energy:

• The energy produced by ATP hydrolysis is known as primary or direct active transport. For instance, the energy is given through the Na+-K+ ATPase (electrogenic pumps). 

• The energy supplied through the electrochemical gradient is enabled by the Symport pumps (such as the Na+-Glucose symporter, lactose permeases, etc.) and Antiport pumps (such as the Na+-Ca2+ antiporter) These are often referred to as secondary or indirect active transport.

Transport of water from roots

Long-distance transportation of water and nutrients in plants takes place through the xylem and phloem. The soil-plant-atmosphere continuum (SPAC) is a pathway that discusses the movement of water from the soil, its transportation to plant parts, and 

the expulsion of water from the plant. Absorption of water in plants occurs through-Passive absorption- when water is absorbed from a higher water potential (in soil) to a lower water potential (in root cells). Active absorption-which occurs due to transpiration.

Ascent of sap

The term “ascent of sap” refers to the movement of water and minerals from the soil to aerial portions like leaves and stems. The cohesion-tension theory, also known as transpirational pull, explains this (Dixon and Jolly, 1894). According to this idea, water from locations with higher water potential (such as the roots) is drawn up, to areas with lower water potential (the leaves)  due to the tension (negative hydrostatic pressure) which is generated by the leaves. There is low water potential in the leaves because they lose water due to the process of transpiration. The water column is kept from collapsing by the cohesive forces of attraction between the water molecules. As a result, water absorption happens to make up for the transpirational loss.

Summary

Intricate transportation networks are needed by plants to enable the interchange of materials and nutrients. The passive process of moving molecules from higher to lower concentrations is known as diffusion. It could be simple (independent) or facilitated transport. Energy is spent during active transport, which is carried out by membrane proteins called transporters and channel proteins. The transpirational pull/cohesion-adhesion principle is used by the roots to absorb water. 

Frequently Asked Questions

1. What do you understand about water potential?
Ans: The potential energy of water per unit volume is referred to as water potential. It describes the amount of water in the atmosphere, plants, and soil.

It is shown as the sum of Osmotic potential, matrix potential, hydrostatic potential, and gravitational potential. 𝜳w = 𝜳𝛑 (osmotic potential)   + 𝜳m (matrix potential)  +𝜳p (hydrostatic potential)  +  𝜳g (gravitational potential).

2. What is the symplastic pathway of water absorption?
Ans: The continuous network of cell cytoplasms is known as the symplastic route.

Through the plasmodesmata connections present between two cells, this pathway allows absorbed water to flow from cell to cell.

3. Which method of water absorption is quick?
Ans: The apoplastic pathway will move more quickly since there won’t be as many obstacles in its path as there are in the symplastic pathway, which is obstructed by Casparian strips and must travel through the protoplasm, which slows down movement.

Introduction

Evolution is an intricate and slow process. Various organisms constantly adapt by changing their morphological and anatomical characteristics in response to the change in the environmental conditions of their habitat. They make minor changes in their genetic composition to adapt to their surroundings and thrive in their niche. These, minor alterations in their genes are responsible for the formation of new species. Adaptive radiation is one such process by which organisms of a single species rapidly transform into distinct forms to propagate successfully and thrive in their niche.

Factors causing adaptive radiation

Various factors are causing adaptive radiation some of them are-

• Geographical isolation– Geographic isolation of organisms from the mainland due to the formation of valleys, mountains, earthquakes, etc. becomes one of the main reasons for adaptive radiation to take place. This sudden separation causes organisms to rapidly adapt to new changes and hence evolve.
• Exposure to new habitat– When organisms are exposed to new habitats, they are exposed to lots of new resources which are available abundantly. This abundance of resources forces them to diversify and adapt in a way that they can exploit those resources to the maximum and thus cause the evolution of new features.
• Changes in environmental conditions- Change in environmental conditions can occur due to floods, volcanic eruptions, deforestation, weather changes, etc. These changes are sudden and hence force the organisms living in particular habitats to change rapidly and hence lead to adaptive radiations.

All of the above factors cause a change in the genetic composition of the organisms and hence lead to the formation of new and permanent changes in their genotype which then in turn leads to the formation of newer species.

Distinctive features of Adaptive radiation

Distinctive features of adaptive radiation which separate it from other evolutionary changes are as follows-

• Common ancestry- Organisms that undergo adaptive radiation belong to the same ancestor. 
• Phenotype-environment correlation- The changes in the phenotype of the species are with the change in the environmental conditions. 
• Trait utility-The new trait thus formed due to adaptive radiation helps the organisms to survive in the new environment. For eg-Darwin’s finches.
• Rapid speciation-This adaptation is a very rapid process as the organisms need to quickly adapt to the changing environment for their survival.

Adaptive radiation in mammals

Adaptive radiation can be studied by various examples once such as limb structure in mammals which is used for locomotion.

• Modern placental mammals are incredibly diverse in terms of size, behavior, and many other features. They may be found practically anywhere in the world.
• These mammals are descended from a little, short-legged, terrestrial predecessor that consumed insects.
• The pentadactyl (five-fingered) small legs belonged to the insectivorous ancestor. Despite being terrestrial, the appendages cannot move the creature.
• The extinction of dinosaurs suddenly caused the remaining mammals to undergo fast diversification. This gave rise to a variety of modern mammals through the process of adaptive radiation.

Mammals followed five separate evolutionary lines and evolved features to fit their respective surroundings, these adaptations are-

• Arboreal placental animals- These are climbers and are generated by growing appendages with grabbing capabilities. Example: Monkeys and tree-dwelling squirrels.
• Aerial placental mammals- These mammals can fly. They evolved limbs into flying wings. Examples- are gliding squirrels and bats.
• Aquatic placental mammals- These can swim in the water. They have appendages that are designed specifically for swimming and surviving in water. Examples- Whales, dolphins, seals, polar bears, sea lions, and walruses.
• Fussorial placental mammals- These are burrowing mammals and bear strong pentadactyl limbs allowing them to dig down far into the ground. Example- moles and badgers.

Cursorial placental mammals- These mammals evolved limbs to allow for swift ground movements such as running, climbing, walking, etc. Examples-wolves, are horses, pigs, antelopes, and lions.

Even though each of the aforementioned groups of placental animals has limbs that are specific for particular habitat, they all shared a common ancestor that had pentadactyl limbs. These evolutionary lines that radiated out in different directions served the purpose of locomotion in their respective habitat.

Summary

Understanding adaptive radiation aids in the comprehension of how organisms interact within a given habitat. Although the food web provides clear knowledge of species interactions, examining adaptive radiation evolution might help us understand how species are dependent on one another. Adaptive radiation enables us to gain new insights into the environmental changes which influence evolution.

Frequently Asked Questions

1. Does adaptive radiation favor biodiversity?
Ans: When a common ancestor diversifies into various forms to fit into the new environment it is known as adaptive radiation. The newly developed adaptive species then gradually diverge from their ancestor until they no longer resemble them. Since adaptive radiation occurs quickly and in multiple directions at once, it leads to biodiversity.

2. How does adaptive radiation operate?
Ans: As a result of being exposed to new ecological conditions, organisms constantly diversify. They do this to take full advantage of the environmental conditions. Therefore, the process of adaptive radiation has been continuously driven by the formation of new ecological niches which increase the availability of newer resources for survival.

3. Is it accurate to say that only species with the ability to move can benefit from adaptive radiation?
Ans: Moving to a new environment is not the only way for an organism to adapt or experience a different environment. Adaptive radiation can also affect sessile plants. For instance, a single common ancestor gave rise to 28 species of Hawaiin silverswords. They belong to three distinct genera and fill various niches.

Introduction

All plants and animals depend on other plants or animals to survive. A example might be a lion consuming a deer or a deer feeding on shrub leaves. In order to depict how energy and nutrients travel through an ecosystem, food chains and food webs were created. In addition to helping us understand the living things that make up an ecosystem, these food chains and webs manage the energy flow within the ecosystem.

Food Chain

A food chain,is simply an orderly series of actions taking place in an environment where one living organism consumes another one. It is a network of living things that makes up an ecosystem and on which each member depends for sustenance and energy.Food chain includes producers, consumers, and decomposers. The producers are the green plants, then the consumers are other animals, the decomposers are the microorganisms.

There are four basic trophic levels in a food chain. They are as follows:

• Sun-The sun is recognised as the fundamental source of nourishment for creating food and supporting growth and development.
• Producers-Green plants are among the producers that make up the first link in the food chain.

Consumers-Any species that eats other organisms is a consumer. This is thought to be the largest part of the food chain in the environment.

• Decomposers-Decomposers are organsisms that decompose the organic content of various plants and animals. They  receive their energy from this organic waste  from the dead objects.

Types of the food chain

There are basically two types of food chain- The terrestrial food chain and the Aquatic food chain. The terrestrial food chain is seen on the land whereas the Aquatic food chain is seen in water bodies. Examples of food chains are given below.

Terrestrial food chain

• Nectar (flowers) → butterflies → small birds → foxes
• Dandelions → snail → frog → bird → fox
• Rice → rat → owl
• Leaves → giraffes → lions → jackals
• Leaves → caterpillars → birds → snakes
• Grass→ antelope → tiger → vulture

Aquatic food chains

• Phytoplankton→Zooplankton→Small fishes→Medium fishes→Mahi mahi→Large sharks

Food web

A system of linked food chains is referred to as a “food web”. A food web is made up of different species from the population. There is a common element throughout all of these, namely the requirement for energy to complete the tasks. Most importantly, the sun is the planet’s main source of energy. Green plants use this energy to create food. Once they have captured the energy, it is next transformed by a variety of local organisms in what is known as a food web.The complex and interrelated food networks that make up the food web can be isolated or separated without impairing the ecosystem’s ability to function. As a result, if one organism is removed from it, the flow of nutrients and energy won’t be impacted. Additionally, they exist in several biomes.The variations in each habitat cause a small variation in each food web.

Types of the food web

• Connected Food Web: Scientists use arrows to illustrate how one species is consumed by another in a connected food chain. Each arrow has the same weight. How effectively one species can eat another is not shown.
• Interaction Food Web : Scientists use arrows to depict one species being consumed by another, just as they do in connected food webs. The weight of the arrows here represents how much one species consumes the other. If one species often consumes another, the arrows shown in such arrangements may be wider, bolder, or darker to reflect the intensity of consumption. The arrow may be very small or not there if the connection between the species is extremely less.
• Energy flow food webs: Food webs that quantify and depict the energy flow between species are used to illustrate the movement of energy and the connections between the organisms in an ecosystem.
• Fossil Food Webs: Just as the food chains that make up an ecosystem can evolve over time, so too might the food webs themselves. Using data from the fossil record, scientists try to reconstruct species relationships in an ancient food web.

Difference between Food web and Food chain

Food chain	Food web
Energy moves from a lower trophic level to a higher one along a single, direct conduit.	The various interconnected food chains are where the ecosystem’s energy flow occurs.
There is only one straight chain in it.	It is made up of numerous interrelated food chains.
Movement of nutrients and energy via a single linear pathway.	Numerous linked channels where nutrients and energy travel.
It rises as a result of the expansion of isolated, small food chains.	Due to the existence of complicated food chains, it grows.
Includes 4-6 trophic levels of various species.	Includes several trophic levels of various species populations.
A single species of lower trophic level organism is fed upon by members of the higher trophic level.	Different kinds of lower trophic level species are consumed by members of higher trophic levels.
If even one group of an organism disrupts, it has an impact on the entire chain.	The removal of one group of species has no effect on the food chain.

Summary

A food chain is a straightforward network that shows the linear movement of nutrients and energy from one trophic level to another. A group of interconnected food chains at different trophic levels is known as a food web.A food web also accurately depicts all the many food chains that are present in an environment.

Frequently Asked Questions

1. Who gave the concept of food web?
Ans: Charles Elton is regarded with originally introducing the concept of a food web, commonly referred to as a food cycle, in the year 1927. In his book named Animal Ecology he gave the concept of food web.

2.What are the components of an arctic food chain?
Ans: An arctic food chain is made up of various organisms such as –

Alage→Planktons→Krill→Artic cod→Leapord Seal→Polar bear.

Here- Algae are the producers, Planktons are primary consumers, Krill, Artic cod and Leapord are secondary consumers and Polar bear is the apex consumer.

3.How energy flows in an terrestrial ecosystem?
Ans: In an terrestrial ecosystem the energy flows from producers to the apex consumers. But the energy goes on decreasing as it moves up  from the producers to the apex consumer. Thus the energy pyramid, here is upright and straight.In this transfer of energy from one tropic levels to the next only 10% of the energy is passed, remaining energy is lost.

Introduction

Environmental changes are natural and will continue to occur from time to time. Change can be abrupt or gradual, like climate change and global warming. Because of the changing environment, some creatures become extinct while certain species can thrive with very minor alterations. These modifications are passed down across generations, enabling the species to adapt to its environment and increase in population. These modifications are known as adaptations. A natural environment where a species grows and reproduces is known as a habitat.

Depending upon various habitats there are the following adaptations–

For more help, you can Refer to Lesson 9 – Living things and habitat in Science Class 6. Check out the video Lesson for a better understanding.

Adaptations in aquatic habitats

Numerous elements, such as light penetration, water composition (nutrient and salt content), oxygen availability, pressure, etc, are various factors that affect life in the aquatic environment. For these purposes, plants and animals are adapted in the following ways-

Plant adaptations-

• Aquatic plants have tissues called aerenchyma to move oxygen from exposed surfaces to low-oxygen submerged sections. 
• Aerenchyma also provides buoyancy to the plant and helps it float and helps to absorb natural light and oxygen.
• The root system is essentially nonexistent because water is all around them. If existent, it is rather small and mostly used for anchorage.
• To endure water currents leaves on submerged plants are typically tiny or ribbon-shaped.
• The stems are tall, hollow, light, and slender.
• Examples include water lilies, sea grass, and lotus.

Animal adaptations-

• Aquatic animals use their gills to breathe.
• Syphons are breathing tubes used by aquatic insects to draw oxygen from the air when submerged in the water. While some creatures, including salamanders, breathe through the skin.
• The blow holes on larger animals like whales and dolphins allow them to take in oxygen as they ascend to the surface and expel carbon dioxide.
• Fish have streamlined bodies to lessen swimming-related water resistance.
• Fins aid in swimming and tails act like rudders to maintain direction.
• Dolphins, whales, fish, etc. are a few examples.

Adaptations in desert habitat

Deserts are dry areas that only get a little rain occasionally throughout the year. It has an arid climate and rocky, sandy soils. Deserts face high temperatures and intense sunlight. For these purposes, plants and animals are adapted in the following ways-

Plant adaptations-

• A common desert adaptation is to conserve body fluids and prevent water loss through transpiration. To stop water loss through transpiration, desert plants’ leaves have thick, waxy cuticles.
• Due to the poor external availability, the stems are fleshy and store a lot of water.
• Desert plants have spines as a kind of defense against herbivores.
• To access deep subterranean water resources, plants have long, deep roots.
• Cacti, and agave, are some examples of desert plants.

Animal adaptations-

• The temperature in the desert is usually very high, hence small organisms have evolved nocturnal behaviors to ensure their survival. At night, when temperatures are generally low, they hunt for prey.
• Many desert animals have skin that is made to keep water from evaporating, and their bodies store lipids which can help them endure prolonged hunger periods.
• High-speed winds frequently carry small sand particles; these animals have large eyelashes, hairy ears, and tight nostrils which prevent sand from getting into their delicate bodily parts.
• Desert animals include kangaroo rats, camels, and desert cats.

Summary

Every living thing is constantly interacting with its environment. The percentage of survivors they have will determine how long the species will exist. Changes in the environment might be gradual or abrupt. However, organisms—whether they be plants or animals—develop specific inherited traits that enable them to adapt to environmental changes. We refer to them as adaptations. Desert-dwelling organisms have developed adaptations that reduce body water loss. Water-dwelling organisms have developed adaptations that help them breathe and adjust to the water pressure. Adaptations help organisms function better and are essential for survival.

Frequently Asked Questions

1. Give some common examples of adaptations.
Ans: Some examples of adaptations are- 

• Pointed teeth and claws of carnivores.
• Varied beak shapes to obtain food.
• Webbed feet of ducks.
• Leaves thick cuticles in xerophytic plants.
• White color fur in arctic animals prevents predation.
• Uricotelism in xerophytic animals.

2. What are Physical, physiological, and Behavioural adaptations?
Ans: Physical adaptations are characteristics that organisms have acquired as a result of their environment. To live in their ecological niche, organisms engage in internal functional mechanisms known as physiological adaptations. Behavioral adaptations are the behaviors or reactions the organism does in response to its surroundings.

3. Describe camouflage.
Ans: The physical adaptation of creatures to resemble or blend into their surroundings to survive attacks from predators is called camouflage.

Introduction 

All species, whether they have one cell or many, engage in diverse metabolic processes. The body produces harmful chemicals as a result of these processes. To prevent excessive accumulation of these waste products in the body, they must be excreted. The excretory system of the body performs the function of eliminating waste. Different species emit different wastes, and they are divided into 3 types- , Uricotelic, and Ammonotelic. The poisonous waste products produced by bodily metabolism must be eliminated from the body and this is done through the process of excretion. 

Excretion

Excretion is the process through which nitrogenous waste is expelled from the body. The excretory system in humans and the majority of chordates is responsible for the process of excretion. The human excretory system consists of two kidneys that filter the blood and remove the primary nitrogenous waste- Urea from the body. Nephrons, the kidney’s functional unit, filter blood and remove urea by the process of urine formation. Excretion is a very important step and it helps in maintaining the homeostasis of the body. Various organisms which stay in the abundance of water have their excretory products in the form of Ammonia and such are called ammonotelic organisms.

 Ammonotelism

• Ammonia is a waste product that some species, including amoeba, protozoa, echinoderms, Platyhelminthes, poriferans, cnidarians, and aquatic mammals, produce.
• These organisms are known as ammonotelic organisms and the process of excretion by such organisms is known as .
• To expel waste from their bodies, these organisms perform diffusion. The waste is excreted through their skin, gills, or kidneys.
• Ammonia has a small molecular size and it easily dissolves in water hence excretion is simple in aquatic animals.
• Elimination of ammonia from the body is very essential because when ammonia dissolves in water it generates ammonium hydroxide, which can result in necrosis of the tissues.
• Ammonotelism is the least energy-consuming and most water-intensive method of excretion. This is so because 1 gram of ammonia requires approx 500ml of water.

Physiological Aspect of Ammonotelic Excretion

• Fish and other aquatic species eat food that is high in protein and other nutrients.
• These organisms are unable to store amino acids for a long period, hence their intestines are designed for the deamination of amino acids.
• Uric acid is created during the process of deamination.
• Uric acid is oxidized which leads to the formation of  Allantoin and allantoic acid.
• Allantoin is hydrolyzed to form allantoate, and subsequent hydrolysis produces urea and glyoxylate.
• Urea is further broken down into ammonia and carbon dioxide in ammonotelic species.
• This ammonia then dissolves with the water and is expelled out of the body. 

Osmoregulation

Osmoregulation is the process of controlling the osmotic pressure of bodily fluids to maintain the water balance of the body. Since the cells of marine creatures are isotonic with saltwater, no regulatory mechanism is necessary. However, to keep the electrolyte balance in the body other organisms’ osmoregulation is a must. Osmoregulation helps maintain salts and water balance in the body. For instance, the antidiuretic hormone (ADH, also known as vasopressin) regulates the content of urine in humans. when the body’s water content is low More water is reabsorbed due to the presence of ADH. This leads to less urine production. More urine is produced when the body’s water content is high. Excretion and osmoregulation work in unison to make sure the steady state of the body is maintained.

Importance of Excretion

Excretion is a very important physiological process of the body. Its significance is given below.

• Excretion helps in the regulation of blood ionic composition.
• It helps in controlling blood pH.
• Regulation of blood volume and blood pressure is done through this process.
• It helps in maintaining blood osmolarity.
• The excretion of waste and foreign substances helps in cleaning the body of toxic and harmful wastes. 
• It assists in the maintenance of osmoregulation in the body.

Summary

Animals’ diets provide them with more amino acids. Ammonia, urea, and uric acid are excretory products that are created during the metabolism of proteins, amino acids, or nucleic acids. Organisms that are ammonotelic release ammonia as a waste product through their gills, skin, and kidneys. Removal of ammonia requires less energy. The regulation of water ion balance and homeostasis depends on the excretion of waste. By controlling the electrolyte balance, every organism keeps its internal environment in a steady state.

Frequently Asked Questions

1. Enlist excretory organs from different organisms.
Ans: Other excretory organs seen in various organisms are-

• Planaria – Flame cells
• Earthworm- Nephridia
• Cockroaches- malpighian tubules
• Prawns- green glands
• Molluscs- Renal glands

2. What are ureotelic and uricotellic organisms?
Ans: Ureotelic organisms – They release Urea as a waste product which is less toxic examples-Mammals and amphibians.

Uricotelic organism- They release Uric acid as a waste product which is the least toxic.  examples- Birds, reptiles, and insects.

3. Only aquatic animals are ammonotelic. Give reasons why?
Ans: Ammonia is highly toxic and hence cannot be stored in an organism’s body. Expulsion of ammonia from the body requires lots of water and hence aquatic animals such as fish only have the ability to form waste products in the form of ammonia.