Biology for Engineers Part I (2023) - Dr. M. Muthukumaran.pptx

Department of Humanities and Social Sciences
Puducherry Technological University, Puducherry – 605014.
BIOLOGY FOR ENGINEERS
Presented By
(Contractual)

Biology for engineering: What is it?
֍ According to the Institute of Biological Engineers ((IBE), it is an
interdisciplinary field of study that uses engineering concepts
along with biological engineers' comprehension of biological
processes to create solution for the various technological
problems.
֍ Some of the specific subfields of biological engineering
includes molecular engineering, soil and water engineering,
physiological engineering, controlled-environment agriculture,
nucleic acid engineering, microbial fuel cells, strength
structures engineering, soil and water engineering, and
bioenergetics and strain factors.
֍ By researching biological processes and merging them with
engineering concepts, biological engineers are able to tackle a
wide range of technical problems.

Source:
https:
//bioe.uw.edu

Source: http://www.artstation.com.
Some Examples

Classification based on
a) Cellularity-unicellular and multicellular
b) Ultra structure prokaryotes and eukaryotes
c) Energy and carbon utilization - Autotrophs, heterotrophs, and
lithotrophs.
d) Ammonia excretion - Aminotelic, Ureotelic, and Uricotelic
e) Habitats-aquatic and terrestrial
e) Molecular taxonomy of three major kingdoms of life.

The cell is the smallest unit of living matter having all the
properties of life.
All organisms are composed of structural and functional
units of life called cells.
The body of some organisms like bacteria, protozoans and
some algae is made up of a single cell ( Unicellular
organisms) while the body of fungi, plants and animals are
composed of many cells (Multicellular organisms).
Cells vary in size and structure as they are specialized to
perform different functions.
But the basic components of the cell are common to all cells.

HISTORY IN DISCOVERY OF CELL
 Robert Hooke (1665), an English scientist, discovered
and coined the term cell while examining a thin slice
of cork under a self-designed compound microscope.
The term cell was derived from a Latin word cellular
(meaning little room or chamber).
 In 1672, Antony Van Leeuwenhoek observed
bacteria, sperms and red blood corpuscles, all of
which were cells.
 In 1831, Robert Brown, an Englishman observed that
all cells had a centrally positioned body which he
termed the nucleus.

Unicellular Organisms:
Types, Characteristics and Examples

Unicellular Organisms:
Types, Characteristics and Examples
Definition:
Unicellular organisms are single-celled organisms. In biology, the term "unicellular organisms"
refers to the type of living entity that they are.
It is single-celled organisms in which the single cell performs functions such as feeding,
locomotion, waste elimination, reproduction, and so on.
In most cases, they are so small that they require a microscope for viewing purposes.

The unicellular category includes the vast majority of life on Earth,
and bacteria accounted as vast majority.
Bacteria, archaea (both prokaryotes), and Eukaryota are the
major groups of single-celled life.
Characteristics of Unicellular Organisms
 Unicellular organisms generally reproduce through asexual means.
 They can be either prokaryotes or eukaryotes.
 They can be found in almost any environment, from hot springs to
frozen tundra.
 For movement, they have whip-like structures.
 Diffusion allows nutrients to enter and exit the cell.

Classification of Unicellular Organisms
Organisms with a single cell are classified into two types based on
the complexity of the cell:
 Prokaryotes
 Eukaryotes
Functions of Unicellular Organisms
 Unicellular organisms reproduce faster than multicellular organisms
due to their asexual nature.
 Unicellular organisms adapt to changing environments more quickly
because only one cell needs to change rather than multiple.
 Unicellular organisms have metabolism and nutritional requirements.
 Unicellular organisms must maintain internal cell conditions.
 The cell moves with a flagellum, or small motor, and performs
multicellular organism functions such as finding food, producing
energy, reproduction and performing various other tasks.

Examples of Unicellular Organisms
 According to evolution theory, unicellular organisms were the first to evolve on
Earth. Their origins can be traced back to 3.8 billion years.
 Each of them has some distinguishing characteristics that aid in adaptation to a
wide range of environmental conditions.
 These single-celled organisms can be found in any habitat, even the most hostile.
Amoeba
 Amoeba is a unicellular, eukaryotic protozoan that can be found in almost all
freshwater environments.
 It is well-known for its unique mode of locomotion. It does not have a specific
shape.
 In fact, the shape of its cells is determined by environmental conditions.
 When necessary, an amoeba extends false feet (pseudopodia) and uses them for
phagocytosis and locomotion.

Paramecium
 Paramecium is a single cell eukaryotic protozoan with a slipper
shape. Its body is covered in minute hair-like cilia that aid in
locomotion and feeding.
 The reproduction of Paramecium is being studied in-depth in order to
better understand the multiplication rate. Under favourable
conditions, it reproduces asexually, whereas, under stressful
conditions, it reproduces sexually.
Bacteria
 Bacteria can be found everywhere in the environment, from the
formation of curd to the transmission of infectious diseases.
 They are tiny and come in a variety of shapes (rod, spherical, spiral,
etc.).

Bacteria
 Some of the bacterial strains have evolved to survive in harsh
environments such as deep within the earth's crust and hot springs.
 They play an important role in nutrient recycling.
Cyanobacteria
 Cyanobacteria, also known as blue-green algae (BGA), is a unicellular
organism. It has characteristics of both bacteria and algae, thus the
name.
 Cyanobacteria and algae are similar in that they both use
photosynthesis to produce food. BGA's prokaryotic nature makes it
similar to bacteria.
Euglena
 Like multicellular organisms, unicellular organisms have a variety of
organelles ranging from cilia to the macro and micronucleus.
 Some single-celled organisms, such as Euglena, use chloroplasts to
generate energy.

Amoeba
Paramecium
Cyanobacteria
Yeast
Bacteria
Source: Google Image

Colonies of Unicellular Organisms
 A colonial organism is a collection of unicellular organisms
living together.
 The difference between a multicellular organism and a colonial
organism is that individual one-celled organisms from a colony
can, if separated, survive on their own, while cells from a
multicellular life-form (e.g., cells from a brain) cannot.
Algae
Volvox

 Multicellular organisms are made of specialized cells which perform different
functions within the organism’s body. e.g. animals are made of different cells
each with a different function (cells in eyes help us to see etc.)
 The entire organism requires all the different types of cells to be present
which perform different functions. The number of cells varies from organism
to organism (e.g. humans have 30-40 trillion cells but C.elegans a
nematode worm only 959 cells), and the individual cells cannot survive
without being a part of the organism.
Multicellular organisms

Characteristics of Multicellular organisms
 An organism that is made of many (multi) cells is called a Multicellular
organism.
 The characteristics of multicellular organisms are as follows
They have bigger bodies as they are made of many cells (e.g. man or
plant).
 The cells in the organism undergo differentiation (convert to different
forms) to form various types of cell.
 Different cells in the same organism perform different functions (e.g
cells in eye help to see, cells in the legs and arms help to move).
 Most of the multicellular organisms are Eukaryotes.
 All the animals and plants are best examples of multicellular organisms.

Examples of Multicellular Organisms
Organs and Tissues
 Multicellular organisms delegate biological responsibilities such as barrier
function, circulation, digestion, respiration and sexual reproduction to
specific organ systems such as the skin, heart, stomach, lungs, and sex
organs.
 These organs are comprised of many different cells and cell types that
work together to perform specific tasks.
 For example, cardiac muscle cells have more mitochondria and
produce adenosine triphosphate to beat together and power the movement
of blood through the circulatory system.
 In contrast, while skin cells have less mitochondria and do have contractile
function, they have tight barrier junction proteins and produce keratin that
creates a barrier protecting the soft inner tissues of the body.

 Organisms made up of more than one cell are categorized as multicellular organisms.
 However, multicellular organisms haven’t always existed. Following the formation of the
Earth, it took one billion years for a unicellular organism to appear on the planet.
 In fact, unicellular organisms existed alone on the Earth for approximately two billion
years before the manifestation of multicellular organisms, which occurred approximately
600 million years ago. While many unicellular organisms choose to reproduce asexually,
many multicellular organisms prefer sexual reproduction.
 Humans, for example, are multicellular organisms created by the fusion of two single
cells specialized for sexual reproduction, commonly referred to as the egg and the
sperm. The fusion of a single egg gamete with a single sperm gamete leads to the
formation of a zygote, or fertilized egg cell.
 The zygote contains the genetic material of both the sperm and the egg. Mitotic division
by the zygote then leads to all the cells of that organism. During development, cell
proliferation and division are followed by specialization with each cell following a
pathway towards differentiation.
 Differentiation allows cells to perform widely different functions in spite of being
genetically identical to one another.
 Thus, all the specialized cells of a multicellular organism, its organs, tissues and that
form nerves, skin cells, respiratory epithelium, and cardiac cells, all originated from the
zygote formed by the merging of two single cell gametes.
Organisms

Which cell type is larger?

Cell Size
Cell Shape
Typical cells range from 5
– 50 micrometers
(microns) in diameter
Variability in cell shape
i.e. spherical, polygonal,
disc like, cuboidal,
columnar,spindle like or
fibre like.

Difference between Unicellular and Multicellular Organisms

Souce:

PROKARYOTIC CELL
 Prokaryotes are unicellular
organisms that lack organelles or
other internal membrane-bound
structures.
 Therefore, they do not have a
nucleus, but, instead, generally
have a single chromosome: a
piece of circular, double-stranded
DNA located in an area of the
cell called the nucleoid.
 Prokaryotes, which were first
observed in 1683 by the inventor
of the Microscope, Antonie van
Leeuwenhoek.
 It’s have sizes that are mostly in
the range 1 to 10.
 Most prokaryotes have a cell wall
outside the plasma membrane.
Structural features of Bacteria and Archeae
Archaea
(Seudo-
Peptidoglycan)

 The composition of the cell wall differs significantly between the domains Bacteria
(Peptidoglycon) and Archaea (Psedo-peptidoglycon), the two domains of life into
which prokaryotes are divided.
 The composition of their cell walls also differs from the eukaryotic cell walls found in
plants (cellulose) or fungi and insects (chitin). The cell wall functions as a protective
layer and is responsible for the organism’s shape.
 Some bacteria have a capsule outside the cell wall. Other structures are present in some
prokaryotic species, but not in others.
 For example, the capsule found in some species enables the organism to attach to
surfaces, protects it from dehydration and attack by phagocytic cells, and increases its
resistance to our immune responses.
 Some species also have flagella used for locomotion and pili used for attachment to
surfaces. Plasmids, which consist of extra-chromosomal DNA, are also present in many
species of bacteria and archaea.
 both prokaryotes, but differ enough to be placed in separate domains.
 An ancestor of modern Archaea is believed to have given rise to Eukarya, the third
domain of life.
 Archaeal and bacterial phyla are shown; the evolutionary relationship between these
phyla is still open to debate.

 Most prokaryotes are bacteria. For example, in Escherichia coli, the genetic material is
present as a long, circular DNA molecule that is compacted into an unenclosed region
called the nucleoid.
 Part of the DNA may be attached to the cell membrane, but in general the nucleoid
extends through a large part of the cell.
 Although the DNA is compacted, it does not undergo the extensive coiling
characteristic of the stages of mitosis, during which the chromosomes of eukaryotes
become visible.
 Nor is the DNA in prokaryotes associated as extensively with proteins as is eukaryotic
DNA. Two bacteria forming by cell division, illustrates the nucleoid regions where the
bacterial chromosomes collect.
 Prokaryotic cells do not have a distinct nucleolus but do contain genes that specify
rRNA molecules.

 Prokaryotic cells lack a defined nucleus, but
have a region in the cell, termed the nucleoid,
in which a single chromosomal, circular,
double-stranded DNA molecule is located.
 Archaeal membranes have replaced the fatty
acids of bacterial membranes with isoprene;
some archaeal membranes are monolayer
rather than bilayer. Basic components are N-
acetylglucosamine and N-
acetyltalosaminuronic acid.
 Prokaryotes can be further classified based
on the composition of the cell wall in terms
of the amount of peptidoglycan present.
 Gram-positive organisms typically lack the
outer membrane found in gram-negative
organisms and contain a large amount of
peptidoglycan in the cell wall, roughly 90%.
 Gram-negative bacteria have a relatively thin
cell wall composed of a few layers of
peptidoglycan (10% peptidoglycon).
 Gram-negative bacteria have a relatively thin
cell wall composed of a few layers of
peptidoglycan. Bacterial peptidoglycan
containing N-acetylmuramic acid.
Bacteria are divided into two major groups: gram-
positive and gram-negative.
Both groups have a cell wall composed of
peptidoglycan: in gram-positive bacteria (90%
peptidoglycon), the wall is thick, whereas in gram-
negative bacteria (10% peptidoglycon), the wall is
thin.
In gram-negative bacteria, the cell wall is surrounded
by an outer membrane that contains
lipopolysaccharides and lipoproteins.
Porins, proteins in this cell membrane, allow
substances to pass through the outer membrane of
gram-negative bacteria. In gram-positive bacteria,
lipoteichoic acid anchors the cell wall to the cell
membrane.

GRAM STRAIN

Plansma membrane structure: Archaeal phospholipids differ from those found in Bacteria and
Eukarya in two ways. First, they have branched phytanyl sidechains instead of linear ones.
Second, an ether bond instead of an ester bond connects the lipid to the glycerol.

FLAGELLA
The bacterial flagellum is a motile organelle composed of thousands of
protein subunits.
The filamentous part that extends from the cell membrane is called the
axial structure and consists of three major parts, the filament, hook, and
rod, and other minor components.

 Mesosome is a convoluted membranous structure formed in a prokaryotic
cell by the invagination of the plasma membrane.
 Its functions are as follows: These extensions help in the synthesis of the
cell membrane, replication of DNA, and protein synthesis.
 a genetic structure in a cell that can replicate independently of the
chromosomes, typically a small circular DNA strand in the cytoplasm of a
bacterium or protozoan. Plasmids are much used in the laboratory
manipulation of genes. Compare with episome.
Mesosome and Plasmids
Mesosome
Plasmids

Functions of Procaryotic Structures

Eukaryotic organisms
Source: https://www.quora.com/Do-plants-and-animal-cells-have-an-endoplasmic-
reticulum

Eukaryotic organisms
 Eukaryotic cells are generally 10 to 100 micrometer in diameter and thus
have a thousand to a million times the volume of typical prokaryotes.
 Eukaryotes (Greek: eu-true; karyonnucleus) possess a well defined nucleus
and are more complex in their structure and function.
 Higher organisms (animals and plants) are composed of eukaryotic cells.
 the eukaryotic cell within the plasma membrane, excluding the nucleus, is
referred to as cytoplasm, and includes a variety of extranuclear cellular
organelles.
 In the cytoplasm, a nonparticulate, colloidal material referred to as the
cytosol surrounds and encompasses the cellular organelles.
 The cytoplasm also includes an extensive system of tubules and filaments,
comprising the cytoskeleton, which provides a lattice of support structures
within the cell.

 Consisting primarily of microtubules made of the protein tubulin and
microfilaments made of the protein actin, this structural framework
maintains cell shape, facilitates cell mobility,and anchors the various
organelles.
 One organelle, the membranous endoplasmic reticulum (ER),
compartmentalizes the cytoplasm, greatly increasing the surface area
available for biochemical synthesis.
 The ER appears smooth in places where it serves as the site for
synthesizing fatty acids and phospholipids; in other places, it appears
rough because it is studded with ribosomes.
 Ribosomes serve as sites where genetic information contained in
messenger RNA (mRNA) is translated into proteins.
 Three other cytoplasmic structures are very important in the eukaryotic
cell’s activities: mitochondria, chloroplasts, and centrioles.
 Mitochondria are found in most eukaryotes, including both animal and
plant cells and are the sites of the oxidative phases of cell respiration.

 These chemical reactions generate large amounts of the energy-rich
molecule adenosine triphosphate (ATP).
 Chloroplasts, which are found in plants, algae, and some protozoans,
are associated with photosynthesis, the major energy-trapping process
on Earth.
 Both mitochondria and chloroplasts contain DNA in a form distinct
from that found in the nucleus. They are able to duplicate themselves
and transcribe and translate their own genetic information. It is
interesting to note that the genetic machinery of mitochondria and
chloroplasts closely resembles that of prokaryotic cells.
 This and other observations have led to the proposal that these
organelles were once primitive free-living organisms that established
symbiotic relationships with primitive eukaryotic cells.
 This theory concerning the evolutionary origin of these organelles is
called the endosymbiont hypothesis.

 Animal cells and some plant cells also contain a pair of complex
structures called centrioles.
 These cytoplasmic bodies, located in a specialized region called the
centrosome, are associated with the organization of spindle fibers
that function in mitosis and meiosis.
 In some organisms, the centriole is derived from another structure,
the basal body, which is associated with the formation of cilia and
flagella (hair-like and whip-like structures for propelling cells or
moving materials). Over the years, many reports have suggested
that centrioles and basal bodies contain DNA, which could be
involved in the replication of these structures.
 This idea is still being investigated. The organization of spindle
fibers by the centrioles occurs during the early phases of mitosis
and meiosis.
 These fibers play an important role in the movement of
chromosomes as they separate during cell division. They are
composed of arrays of microtubules consisting of polymers of the
protein tubulin.

Features Prokaryotic Eukaryotic
Size
Size of cell is 1-2µm by 1-4µm or
less.
Greater than 5 µm in diameter.
Cell type
Mostly unicellular (some
cyanobacteria may be multicellular).
Mostly multicellular.
Nucleus
True nucleus is absent. Nucleus lack
nuclear membrane and nucleolus.
Such nucleus is called nucleoid.
Nuclear membrane and nucleolus are
present.
Chromosome
Usually single circular without
histones.
Multiple linear with histones.
Genes Expressed in groups called operons. Expressed individually.
Zygote Merozygotic (partially diploid). Diploid.
Cell division Binary fission of budding Involves mitosis.
Sexual reproduction No meiosis. Transfer of DNA only. Involves meiosis.
Permeability of nuclear
membrane
Absent. Selective.
Cytoplasmic streaming Absent Present
Cytoskeleton Absent Present
Pinocytosis Absent Present
Gas vacuoles Can be present Absent
Mesosome
Present. Performs the function of
Golgi bodies and mitochondria and
also help in the separation of
chromosome during cell division.
Absent
Ribosome
Smaller size 70S, distributed in the
cytoplasm.
Larger size 80s, found on membranes
as in endoplasmic reticulum; 70s
present in organelles such as
chloroplast and mitochondria.
Difference between Prokaryotic and Eukaryotic r Organisms

Mitochondria Absent Present
Chloroplast Absent Present
Endoplasmic Reticulum Absent Present
Golgi structure Absent Present
Membrane bound vacuoles Absent Present
Lysosomes and peroxisomes Absent Present
Microtubules Absent or rare Present
Flagella
Simple structure composed of protein,
flagellin.
Complex with 9+2 structure of tubulin and
other protein.
Plasma membrane
Generally lack sterol and no carbohydrate.
Contain part of respiration and in some
photosynthetic machinery.
Sterol and carbohydrate is present that serve
as receptors.
Do not carry out respiration and
photosynthesis.
Glycocalyx Present as a capsule or slime layer. Present in some cells that lack cell wall.
Cell wall
Usually present. Chemically complex
(typical bacterial cell wall includes
peptidoglycan).
When present, chemically simple (includes
cellulose and chitin).
Extrachromosomal plasmid
Present. Nonessential prokaryotic genes are
encoded on extra chromosomal plasmid.
Absent
Transcription and translation Occur simultaneously.
Transcription occurs in nucleus and then
translation occurs in cytoplasm.
Respiration Many strict anaerobes.
All aerobic, but some facultative anaerobes
by secondary modification.
Photosynthetic enzymes
Bound to plasma membrane as composite
chromatophores.
Enzymes packed in plastids bound by
membrane.
Nitrogen fixation Some possess this ability. None possess this ability.
Metabolic mechanism Wide variation
Glycolysis, electron transport chain, Krebs
cycle.
Duration of cell cycle Short, takes 20-60 minutes to complete. Long, takes 12-24 hours to complete.
DNA base ratio as mol% of
Guanine+ Cytosine (G+C %)
28-73 About 40

ENERGY AND CARBON SOURCE
Lithotrophs
Photo-Lithotrophs Chemo-Lithotrophs
Chemical in
the form of
electron
Obtain Inorganic in
the form of electron
by light effect
Obtain Inorganic in
by chemicals

 In physics, energy is the ability to perform work. It could exist in several different
forms, such as potential, kinetic, thermal, electrical, chemical, radioactive, etc.
 The two main ways that organisms obtain energy are through exposure to light or
chemical oxidation.
 The source of carbon that an organism uses for metabolism and its energy source
can be used to identify it. Auto- ("self") and hetero- ("other") are prefixes that
allude to the origins of the carbon sources that different organisms can employ.
 Autotrophs are organisms that transform inorganic carbon dioxide (CO2) into
organic carbon molecules. Plants and cyanobacteria are well-known examples of
autotrophs.
 Contrarily, the more intricate organic carbon compounds that autotrophs first give to
heterotrophs serve as their source of nutrition.
 Numerous species, from humans to many prokaryotes like Escherichia coli, are
heterotrophic are well known.

Definition: These organism synthesize all their food from inorganic substances (H2O, C02,
H2S salts).
The autotrophic bacteria are of two types:
(i) Photoautotrophs
•These organism like bacteria capture the energy of sunlight and transform it into the
chemical energy.
•In this process, CO2 is reduced to carbohydrates.
•The hydrogen donor is water and the process produce free oxygen.
•Photoautotroph has Chlorophyll pigment in the cell and its main function is to capture
sunlight e.g., Cyanobacteria.
•Some photoautotrophic bacteria are anaerobes and have bacteriochlorophyll
and bacteriovirdin pigments respectively.
Autotrophic organism
•These oranism like bacteria do not require light (lack the light phase but have the dark
phase of photosynthesis) and pigment for their nutrition.
•These bacteria oxidize certain inorganic substances with the help of atmospheric oxygen.
•This reaction releases the energy (exothermic) which is used to drive the synthetic
processes of the cell (Ex. Thiobacillus ferrooxidans).
(ii) Chemoautotrophs

Definition: The heterotrophic organism obtain their-ready made food from organic
substances, living or dead. Most of pathogenic bacteria of human beings, other plants and
animals are heterotrophs. Some heterotrops have simple nutritional requirement while
some of them require large amount of vitamin and other growth promoting substance.
Such organisms are called fastidious heterotrophs.
Heterotrophic bacteria are of two types:
a. Photoheterotrophs
These organism like bacteria can utilize light energy but cannot use CO2 as their sole
source of carbon.
They obtain energy from organic compounds to satisfy their carbon and electron
requirements. Bacteriochlorophyll pigment is found in these bacteria.
eg., Purple non-sulphur bacteria (Rhodospirillum, Rhodomicrobium, Rhodopseudomonas
palustris).
b. Chemoheterotrophs
Chemoheterotrophs obtain both carbon and energy from organic compounds such as
carbohydrates, lipids and proteins.
Glucose or Monosaccharide [(CH2O)n] + O2 → CO2 + H2O + Energy
There are three main categories that differ in how chemohetrotrophs obtain their organic
nutrients:(i) Saprophytic bacteria.
(ii) Parasitic bacteria.
(iii) Symbiotic bacteria.
Heterotrophic organism

Lithotrophs:
Some organisms can use reduced organic compounds as electron donors and are
termed as Lithotrophs.
They can be Chemolithotrophs and Photolithotrophs.
Photo-lithotrops: These bacteria gain energy from light and use reduced inorganic
compounds such as H2S as a source of electrons. eg: Chromatium okeinii.
Chemo-lithotrophs: These bacteria gain energy from reduced inorganic compounds
such as NH3, H2S, Fe2 as a source of electron eg; Nitrosomonas.

Classifications of Organisms by Energy and Carbon Source
Classifications Energy Source Carbon Source Examples
Chemotrophs
Chemoautotrophs Chemical Inorganic
Hydrogen-, sulfur-,
iron-, nitrogen-, and
carbon monoxide-
oxidizing bacteria
Chemoheterotrophs Chemical Organic compounds
All animals, most
fungi, protozoa, and
bacteria
Phototrophs
Photoautotrophs Light Inorganic
All plants, algae,
cyanobacteria, and
green and purple
sulfur bacteria
Photoheterotrophs Light Organic compounds
Green and purple
nonsulfur bacteria,
heliobacteria
Lihotrophs
Photolithotrophs Light
Obtain Inorganic in
by light effect
Chromatium okei
nii.
Chemolithotrophs Chemical
Obtain Inorganic in
by chemicals
Nitrosomonas

INTRODUCTION
Removal of waste products from the body is called excretion.
Waste products are synthesized in the cells due to metabolic
activity.
Excretion is an essential process in all forms of life. In one
celled organisms, waste are discharged through the surface of
the cell. The higher plants eliminate gases through the stomata
or pores present on the leaf surface. Multicellular animals have
special excretory organs.
Ammonia, urea and uric acid are the major forms of nitrogenous
wastes excreted by the animals.
Ammonia is the most toxic form and requires a large amount of
water for its elimination, whereas uric acid, being the least toxic,
can be removed with a minimum loss of water.
On the basis of main excretory products, animals can be divided
into 3 groups – ammonotelic, ureotelic and uricotelic
(described later).
EXCRETION

•In humans, primary excretory organs are kidney (described later) and accessory
excretory organs are lung, liver, skin (sebaceous gland) and intestine.
•Our lungs remove large amounts of CO2 (18 litres/day) and also significant quantities
of water every day.
•Liver, the largest gland in our body, secretes bile-containing substances like bilirubin,
biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs. Most of these
substances ultimately pass out alongwith digestive wastes.
•Sebaceous glands eliminate certain substances like sterols, hydrocarbons and waxes
through sebum. This secretion provides a protective oily covering for the skin.
•Intestine – Excess salt of calcium, magnesium and iron are excreted by epithelial cells
of colon (large intestine) along with faeces.
•Excretory organs in other animals are – protonephridia, nephridia, malpighian tubules,
antennal glands etc.
Protonephridia or flame cells are the excretory structures in platyhelminthes
(flatworms, e.g., Planaria), rotifers, some annelids and the cephalochordate -
Amphioxus. Protonephridia are primarily concerned with ionic and fluid volume
regulation i.e., osmoregulation.
Nephridia are the tubular excretory structures of earthworms and other annelids.
Nephridia help to remove nitrogenous wastes and maintain a fluid and ionic
balance.
Malpighian tubules are the excretory structures of most of the insects including
cockroaches. Malpighian tubules help in the removal of nitrogenous wastes and
osmoregulation.
EXCRETORY ORGANS

Table : Excretory organs of different organisms
(Invertebrates)

Habitats – Aquatics and
Terrestrial organisms

Habitat ecology. It deals with the study of different habitats of the biosphere.
According to the kind of habitat, ecology is subdivided into marine ecology,
freshwater ecology, and terrestrial ecology. The terrestrial ecology too is
further subdivided into forest ecology, cropland ecology, grassland ecology,
etc., according to the kind of study of its different biomes.
Habitat: The living organism and their surroundings
 Different types of living organism are found in different regions of the world.
In this article, we will be studying about different kinds of living creatures and
how they survive in different types of climate.
How is the habitat different for different living organisms?
 Certain characteristic of living organisms which enables them to survive in
their surrounding are known as an adaptation in living organism.
 The surrounding where living organisms survive is known as habitat.

Definition: Habitat is a part of an ecosystem. The climate, plants, and
animals are the identities of a habitat. Ecosystems primarily have
two domains:
1. Terrestrial or Land ecosystem
2. Aquatic or Water ecosystem.
Habitat – Aquatic Ecosystem
Types of Ecosystem

Aquatic habitat
Plants and animals that live under
water.
Types:
Ponds:
Plants with their roots fixed in the soil.
Plants whose roots are totally
submerged in water.
Oceans:
Animals have gills which help them
in the utilization of dissolved
oxygen in the water.
Some animals like whales and
dolphins have nostrils to breathe.

 They cover only a small portion of earth nearly 0.8 per cent. Freshwater
involves lakes, ponds, rivers and streams, wetlands, swamp, bog and
temporary pools. Freshwater habitats are classified into lotic and lentic
habitats. Water bodies such as lakes, ponds, pools, bogs, and other
reservoirs are standing water and known as lentic habitats. Whereas lotic
habitats represent flowing water bodies such as rivers, streams.
 Plants and animals in an aquatic ecosystem show a wide variety of
adaptations which may involve life cycle, physiological, structural and
behavioural adaptations. Majority of aquatic animals are streamlined which
helps them to reduce friction and thus save energy. Fins and gills are the
locomotors and respiratory organs respectively.
 Special features in freshwater organisms help them to drain excess water
from the body. Aquatic plants have different types of roots which help them
to survive in water. Some may have submerged roots; some have emergent
roots or maybe floating plants like water hyacinths.
Aquatic Ecosystem

A. Water supports many lives. Organisms which survive in
water are called aquatic organisms. Eg: Fish, crabs,
toads, plants etc., these are all aquatic organisms. They
depend on water for their food, shelter, reproduction and
all other life activities.
B. An aquatic ecosystem includes a group of interacting
organisms which are dependent on one another and
their water environment for nutrients and shelter.
Examples of aquatic ecosystem include oceans, lakes
and rivers.
C. An aquatic ecosystem includes freshwater habitats like
lakes, ponds, rivers, oceans and streams, wetlands,
swamp, etc. and marine habitats include oceans,
intertidal zone, reefs, seabed and so on. The aquatic
ecosystem is the habitat for water-dependent living
species including animals, plants, and microbes.

 They mainly refer to the rapidly flowing waters that move in a unidirectional way including the rivers
and streams.
 These environments harbor numerous species of insects such as beetles, mayflies, stoneflies and
several species of fishes including trout, eel, minnow, etc.
 Apart from these aquatic species, these ecosystems also include various mammals such as beavers,
river dolphins and otters.
 They include all standing water habitats. Lakes and ponds are the main examples of Lentic Ecosystem.
 The word lentic mainly refers to stationary or relatively still water. These ecosystems are home to algae, crabs, shrimps,
amphibians such as frogs and salamanders, for both rooted and floating-leaved plants and reptiles including alligators
and other water snakes are also found here.
 Wetlands are marshy areas and are sometimes covered in water which has a wide diversity of plants and animals.
Swamps, marshes, bogs, black spruce and water lilies are some examples in the plant species found in the wetlands.
The animal life of this ecosystem consists of dragonflies and damselflies, birds such as Green Heron and fishes such
as Northern Pike.
Lotic Ecosystems
Lentic Ecosystems
Wetlands

 Marine ecosystem covers the largest surface area of the earth. Two third of earth is covered by
water and they constitute of oceans, seas, intertidal zone, reefs, seabed, estuaries, hydrothermal
vents and rock pools.
 Each life form is unique and native to its habitat. This is because they have adaptations according
to their habitat. In the case of aquatic animals, they can’t survive outside of water.
 Exceptional cases are still there which shows another example of adaptations (e.g. mudskippers).
The marine ecosystem is more concentrated with salts which make it difficult for freshwater
organisms to live in. Also, marine animals cannot survive in freshwater. Their body is adapted to
live in saltwater; if they are placed in less salty water, their body will swell (osmosis).
 Ocean Ecosystems
Our planet earth is gifted with the five major oceans, namely Pacific, Indian, Arctic, and the
Atlantic Ocean. Among all these five oceans, the Pacific and the Atlantic are the largest and
deepest ocean. These oceans serve as a home to more than five lakh aquatic species. Few
creatures of these ecosystems include shellfish, shark, tube worms, crab small and large ocean
fishes, turtles, crustaceans, blue whale, reptiles, marine mammals, seabirds, plankton, corals and
other ocean plants.
 Coastal Systems
They are the open systems of land and water which are joined together to form the coastal
ecosystems. The coastal ecosystems have a different structure, and diversity. A wide variety of
species of aquatic plants and algae are found at the bottom of the coastal ecosystem. The fauna is
diverse and it mainly consists of crabs, fish, insects, lobsters snails, shrimp, etc.
Marine Aquatic Ecosystem
Mangroves: This ecosystem revolves around mangrove trees, which is a non-taxonomic classification for trees and shrubs that can live in wet,
saline habitats. Mangrove ecosystems are found on a quarter of the world's tropical shorelines. This environment is a breeding ground for many
species of fish and birds, and is diverse in specialized plant species.

Terrestrial habitat

Types of habitat:
Different types of habitats are: 1. Terrestrial habitat 2. Aquatic habitat
1) Terrestrial habitat:
Plants and animals that survive on land.
Three types:
•Desert: At night, small animals stay out, while in the day they stay
inside the deep holes in the sand.
Plants do not have leaves. Photosynthesis takes place
through stems.
•Mountain: Plants are cone shaped, and leaves have needle-like
structure. Animals have thick fur to protect them from cold.
•Grassland: Brown in color, found in the grassy area.

 The three- domain system is a biological classification which was introduced
by Carl Woese, a professor in the department of microbiology, university of Illinois,
Urbana- Champaign in 1990 that divides cellular life forms into archaea,
bacteria and eukarya domains.
 It emphasizes the separation of prokaryotes into two groups, originally called
eubacteria (now bacteria) and archaebacteria (now archaea) because of their
fundamental differences, Woese argued that each of the two arose separately from
an ancestor with poorly developed genetic machinery, often called a progenote.
 In fact the three-domain system is loosely based on the traditional five- kingdom
system but divides the monera into two ‘’domains’’, leaving the remaining eukaryotic
kingdoms in the third domain.
It is actually a six kingdom classification.
Archaea domain: The demain contains prokaryotic organisms which have a monolayer
core of lipids in the cell memebrane and distinct nucleotides in their 16S RNA. It
contains a single kingdom
Bacteria domain: The domain contains prokaryotes which lack membrane covered cell
organelles but do have a sort of micro chambers for separating various activities. There
is a single kingdom.
Three Domains of Life (Six Kingdom Classification) – 1990

Three domain of Six Kingdoms in
Living Things

Kingdom archaebacteria
The kingdom contain early prokaryotes which live in extreme environments,
For Example:
 (a) Methanogens - metabolize hydrogen and carbon dioxide into
methane.
 (b) Halophiles - live in salt.
(c) Thermoacidophiles – live in acid high temperatures (upto 110 degrees Celsius).

Archaebacteria domain
They are a group of most primitive prokaryotes which are believed
to have evolved immediately after theevolution of the first life.
They have been placed in a separate subkingdom or domain of
archae by a number of workers (e.g., woese, 1994).
Archaebacteria are characterised by absence of peptidoglucan in
their wall. Instesd the wall contains protein and
noncellulosicpolysaccharised (Pseudopeptidoglucon).
It has pseudomurein in some methanogens.

Eubacteria domain
A. The domain contains diverse type of bacteria having
peptidoglycan cell wall, glycogen as food reserve,naked DNA
coiled to form nucleoid, absence of sap vacuoles and presence
of 70S ribosomes.
B. Some common group are bacteria, mycoplasma, ctinomycetes,
rickettsiae, spirochaetes, firmicutes, cyanobacteria.
The domain contains eukaryotic organisms which originated by
endosymbiotic association between some archaebacteria and
eubacteria. It has four kingdoms- protista, fungi, plantae and
animalia.
Eukarya domain

Exam View

6. Lehinger Principles of Biochemistry, Lehinger. 6th edition.
7. Rapid biology, Reena Ahiawat, 1-695.
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