Classification of Organisms

I. Classification

A. Arrangement in classes or groups

to improve communication

between scientists.

B. Four factors used to classify

1. They have similar structures.

2. They have similar behaviors.

3. They eat the same kinds of things.

4. They have the same chemical make up.

Biological Classification of Plants and Animals

Biological classification of plants and animals was first

proposed by Aristotle on the basis of simple morphological

characters.

Linnaeus later classified all living organisms into two

kingdoms – Plantae and Animalia.

Whittaker proposed an elaborate five kingdom classification

– Monera, Protista, Fungi, Plantae and Animalia

The main criteria of the five kingdom classification were cell

structure, body organisation, mode of nutrition and

reproduction, and phylogenetic relationships [evolutionary

development and diversification of a species].

Kingdoms

At present, the biological classification

includes:

Kingdom Monera

Kingdom Protista

Kingdom Fungi

Kingdom Plantae

Kingdom Animalia

Viruses, Viroids and Lichens

II. Five Kingdoms of Living

Things

A. Moneran Kingdom1. Simple single celled

Example: Bacteria

2. Helpful types

a. Decomposers

b. Yogurt

3. Harmful types

a. Pathogens – cause disease

b Strepthroat

Monera

Archaebacteria

Eubacteria

Photosynthetic bacteria

Chemosynthetic bacteria

Heterotrophic bacteria

Reproduction

Mycoplasma

The organisms in this group are

prokaryotes == do not have a defined nucleus or organelles

unicellular == do any of them show multi-cellular body

designs.

This group includes all Some well-known

bacteria include blue-green algae or

cyanobacteria [have cell walls], and mycoplasma

[doesn’t possess a Cell Wall].

They are the most abundant micro-organisms

and live in extreme habitats.

Some of them have cell walls [bacteria] while

some do not [mycoplasma].

The mode of nutrition of organisms in this group

can be either by synthesizing their own food

(autotrophic) or getting it from the environment

(heterotrophic). Many of them live in or on other

organisms as parasites.

the spherical Coccus

the rod-shaped Bacillus

the comma-shaped Vibrium

the spiral Spirillum

Some of the bacteria are autotrophic, i.e., they synthesise

their own food. They may be photosynthetic autotrophic

or chemosynthetic autotrophic (metabolic synthesis of

organic compounds by living organisms using energy

derived from reactions involving inorganic chemicals).

Archaebacteria

These bacteria are special since they live in some of the

most harsh habitats such as extreme salty areas

(halophiles),hot springs (thermoacidophiles) andmarshy

areas (methanogens).

Archaebacteria differ from other bacteria in having a

different cell wall structure and this feature is responsible

for their survival in extreme conditions.

Methanogens are present in the gut of several ruminant

animals such as cows and buffaloes and they are

responsible for the production of methane (biogas) from

the dung of these animals

Eubacteria

There are thousands of different eubacteria

or ‘true bacteria’.

They are characterized by the presence of a

rigid cell wall, and if motile, a flagellum

Photosynthetic bacteria

The cyanobacteria (also referred to as blue-green algae)

have chlorophyll a similar to green plants and are

photosynthetic autotrophs.

The cyanobacteria are unicellular, colonial, filamentous,

freshwater/marine or terrestrial algae. The colonies are

generally surrounded by gelatinous sheath.

They often form blooms [algal blooms] in polluted water

bodies.

Some of these organisms can fix atmospheric nitrogen in

specialized cells called heterocysts, e.g., Nostoc and

Anabaena.

Chemosynthetic bacteria

Chemosynthetic autotrophic bacteria

oxidise various inorganic substances such as

nitrates, nitrites and ammonia and use the

released energy for their ATP production.

They play a great role in recycling

nutrients like nitrogen, phosphorous, iron

and sulphur.

Heterotrophic bacteria

Heterotrophic bacteria are the most abundant in nature. The majority

are important decomposers.

Many of them have a significant impact on human affairs. They are

helpful in making curd from milk, production of antibiotics, fixing

nitrogen in legume roots, etc.

Some are pathogens causing damage to human beings, crops, farm

animals and pets.

Cholera, typhoid, tetanus, citrus canker are well known diseases

caused by different bacteria.

Reproduction

Bacteria reproduce mainly by fission.

Sometimes, under unfavorable conditions,

they produce spores.

They also reproduce by a sort of sexual

reproduction by adopting a primitive type

of DNA transfer from one bacterium to the

other.

Kingdom Protista

1. Complex , single celled organism

a. Euglenas- make their own food

b. Protozoans – depend on getting food from

other sources.

c. Examples of common

protists are as follows

Trypanosoma use flagellum to move

Peramecium have hair like structures called cilia

Here is an Ameba with its pseudopods

Protista

All single-celled eukaryotes are placed under Protista

Boundaries of this kingdom are not well defined. This

kingdom forms a link with the others dealing with plants,

animals and fungi.

It includes Chrysophytes, Dinoflagellates, Euglenoids,

Slime moulds and Protozoans. Examples are unicellular

algae, diatoms and protozoans.

Their mode of nutrition can be autotrophic or

heterotrophic.Members of Protista are primarily aquatic.

Some have flagella or cilia that helps in movement.Protists

reproduce asexually and sexually by a process involving

cell fusion and zygote formation.

Chrysophytes

This group includes diatoms and golden algae

(desmids).Most of them are photosynthetic.

Diatoms are the chief ‘producers’ in the oceans.

They are found in fresh water as well as in marine

environments. They are microscopic and float

passively in water currents (plankton).

Dinoflagellates

These organisms are mostly marine and photosynthetic.

They appear yellow, green, brown, blue or red depending

on the main pigments present in their cells.

The cell wall has stiff cellulose plates on the outer surface.

Most of them have two flagella; one lies longitudinally

and the other transversely in a furrow between the wall

plates.

Euglenoids

Majority of them are fresh water organisms

found in stagnant water.

Instead of a cell wall, they have a protein rich

layer called pellicle which makes their body

flexible.

They have two flagella, a short and a long

one.Though they are photosynthetic in the

presence of sunlight, when deprived of sunlight

they behave like heterotrophs by predating on

other smaller organisms

Slime Moulds

Slime moulds are saprophytic protists.

The body moves along decaying twigs and leaves

engulfing organic material.

Under suitable conditions, they form an aggregation called

plasmodium which may grow and spread over several

feet.

During unfavorable conditions, the plasmodium

differentiates and forms fruiting bodies bearing spores at

their tips. The spores possess true walls. They are

extremely resistant and survive for many years, even under

adverse conditions. The spores are dispersed by air

currents.

Protozoans

All protozoans are heterotrophs and live as

predators or parasites. They are believed

to be primitive relatives of animals. There

are four major groups of protozoans.

Amoeboid protozoans (Amoeba)

Flagellated protozoans (Trypanosoma)

Ciliated protozoans (Paramoecium)

Sporozoans (Plasmodium (malarial

parasite)

C. The Fungi Kingdom

1. Many celled organisms

a. Sprophytes- eat dead things

2. Depend on others for

food

b. Parasites – attack living tissues

3. Examples of

a. Yeastsb. Mushrooms

Kingdom Fungi

These are heterotrophic eukaryotic organisms.Most

fungi are heterotrophic and absorb soluble organic matter

from dead substrates and hence are called saprophytes.

Those that depend on living plants and animals are called

parasites.Some fungal species live in permanent mutually

dependent relationships with bluegreen algae (or

cyanobacteria).

Such relationships are called symbiotic. These symbiobic

life forms are called lichens. They can also live as

symbionts in association with roots of higher plants as

mycorrhiza.Fungi + Bluegreen algae (Cyanobacteria) ==

Lichens.

Phycomycetes( Rhizopus -the bread mould)

Ascomycetes (yeast)

Basidiomycetes (mushrooms)

Deuteromycetes(imperfect fungi because only the

asexual or vegetative phases of these fungi are known)

A picture of Bread Mold

And here is a Mushroom

»D. The Plant Kingdom1. Many celled organism

2. They make their own food.

–a. Process called photosynthesis

–b. Examples: –Trees, flowers, and grass

Kingdom Plantae

These are multicellular eukaryotes with cell

walls mainly made of cellulose.

They are autotrophs and use chlorophyll for

photosynthesis.

A few members are partially heterotrophic such as

the insectivorous plants or parasites.

Bladderwort and Venus fly trap are examples of

insectivorous plants and Cuscuta is a

parasite.Plantae includes algae, bryophytes,

pteridophytes, gymnosperms and angiosperms.

Life cycle of plants has two distinct phases

– the diploid sporophytic and the haploid

gametophytic – that alternate with each

other.

Kingdom Animalia

These include all organisms which are multicellular

eukaryotes without cell walls.

They are heterotrophs.They directly or indirectly depend

on plants for food. They digest their food in an internal

cavity and store food reserves as glycogen or fat.

Their mode of nutrition is holozoic – by ingestion of

food.They follow a definite growth pattern and grow into

adults that have a definite shape and size.

Higher forms show elaborate sensory and

neuromotor mechanism. Most of them are

capable of locomotion.The sexual

reproduction is by copulation of male and

female followed by embryological

development.

1. Many Celled Organisms

2. Consume other Organisms for food

3. The Subdivision of this Kingdom

a. Naming Organisms

b. Common names – house cat

c. Scientific Names – Felis catus

Genus Species

d. How are scientific names made?

4. How Kingdoms are subdivided

a. Phylum Tracheophyta

b. Class Angiospermae

c. Order Dicotyledon

d. Family Ranunculaceae

e. Genus Aquilegia

f. Species cearulea

1. Phylum: Porifera – The Spongesa. Sessile (permanently attached

as adults.)b. Pores

c. Two cell layers

d. Both marine and fresh water

e. Respiration- Oxygen absorbed by

inner cells.f. Digestion- Food absorbed by inner

cell layer.

g. Circulation-

1. Flagellum create a water

current.

2. No Blood

2.Phylum: Coelenterata

Jellyfish and Coral

a. They have tentacles.

b. They have stinging cells.

c. Some are sessile/ some free-living

d. Respiration – Oxygen absorbed by inner cell layer

e. Digestion –1. Food absorbed by inner cell wall

2. Single opening mouth

f. Circulation – water current distributes

gas/food

3. Phylum: Platyhelminthes –

The Flatworms

a. Parasites live off host

b. They can regenerate if

broken.

c.Respiration – Oxygen absorbed through the skin

d. Digestion -1. Nutrients absorbed into the skin

2. Single opening mouth

e. Circulation – Nutrients/ gas circulated by host

4. Phylum Nematoda - Roundworms

a. Many are parasites / some free - living

b. Respiration – Oxygen absorbed through the skin

d. Digestion

1. Nutrients absorbed by inner

cell layer.

2. Complete system

( Two Openings)

D. Circulation - Food / gas absorbed through cells

5. Phylum Annelida -

The Segmented Worm

a. Segmented body

b. Respiration – Gas exchange through the

skin.

c. Digestion –

1. Specialized organs

2. Complete System

3. Nutrients absorbed through inner

cell layer.

d. Circulation – Pairs of “hearts” circulate blood

5. Phylum Annelida - The Segmented Worm cont

e. Example : Earthworm - Nightcrawlers

6. Phylum: Mollusca – The Mollusks

a. Mostly Shell-builders

b. Mantle – Fleshy covering

that secretes the shell.

c. Well developed sense organs

6. Phylum: Mollusca – The Mollusks

d. Respiration – Gills for gas exchange

e. Digestion – complete with specialized organs.

f. Circulation – hearts for pumping blood.

g. Mostly aquatic

h. Examples

Octopus ,squid,

Snails and clams

7. Phylum - Arthropoda

7. Phylum Arthropods

a. Exoskeleton (outside)

b. Jointed legs

c. Segmented body

d. Circulation – open, hearts for pumps

e. Respiration -

1. Vents and spiracles ( land arthropods)

2. Gills (aquatic arthropods)

f. Digestion – complete with specialized organs

g. Five classes of arthropods

g. Arthropods five classes cont.

1. Class Crustacea ( crabs, lobsters)

a. Mostly marine (salt water)

b. Cephalothorax and abdomen

(two body regions)

c. Five pair of legs

g. Arthropods five classes cont.

2. Class Arachnida (spiders, ticks, mites)

a. Many are poisonous

b. Two body regions

c. Four pairs of legs

g. Arthropods five classes cont

3. Class Insecta ( grasshoppers, bees)

a. Many fly

b. Three body regions

c. Three pairs of legs

g. Arthropods five classes cont

4. Class Chilopoda ( centipedes)

a. Many segments

b. One pair of legs per segment

c. Poisonous

g. Arthropods five classes cont

5. Class Diplopoda ( millipedes)

a. Many segments

b. Two pairs of legs per segment

c. Not poisonous

8.Phylum: Echinodermata

starfish

A. Spiny skin

B. Radial design

C. Examples: sea stars

9.Phylum Chordata

( vertebrates with spinal cords)

A. Circulatory system

1. Closed (veins and arteries)

2. Multi chambered heart

B. Digestive System –

Complete system with specialized organs

C. Respiratory System

1. Lungs on land

2. Gills in most cases in water

Phylum: Chordata

7. Class: Mammalia cont.

d. Mammary glands

- produce milk

- nurse young

e. Two pairs of limbs

f. High functioning brain and sense organs

Virus

Viruses did not find a place in classification

since they are not truly ‘living’, if we

understand living as those organisms that

have a cell structure.The viruses are non-

cellular organisms that are characterized by

having an inert crystalline structure outside

the living cell.

Viroids

Viroids are infectious agents that are

smaller than viruses. A viroid was found to

be a free RNA; it lacked the protein coat

that is found in viruses, hence the name

viroid. The RNA of the viroid was of low

molecular weight. Viroids caused potato

spindle tuber disease.

Lichens

Lichens are symbiotic associations i.e.

mutually useful associations, between algae

and fungi.The algal component is known as

phycobiont and fungal component as

mycobiont, which are autotrophic and

heterotrophic, respectively.Algae prepare

food for fungi and fungi provide shelter and

absorb mineral nutrients and water for its

partner.