Download SUMMARY Module 1: Characteristics, Classification and Diversity of

SUMMARY
Module 1: Characteristics, Classification and Diversity of Living Organisms
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You learned that an individual living thing is called an organism. The term organisms is
used to describe something which have all the characteristics of a living thing.
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Living organisms are different from non-living things in the way that all living things share
seven characteristics. The seven characteristics are:
- Organisms reproduce
- Organisms grow
- Organisms feed
- Organisms respire
- Organisms excrete
- Organisms move
- Organisms are sensitive.
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Classification is the grouping of organisms according to their structural similarities.
These groups can be arranged from the largest to the smallest group, they are arranged
in Kingdom, Phylum, Class, Order, Family, Genus and Species.
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Kingdoms are the highest class for all living organisms and are divided into five kingdoms
(Prokaryotes, Protoctista, Fungi, Plants and Animals). Organisms in a kingdom has
broader features to group them together, but organisms that are in the species group,
has more specific features that group them together.
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A species can be defined as a group of organisms with similar features, which are
capable of breeding and producing fertile offspring.
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Classification hierarchy helps scientists to sort organisms in order, to identify new
organisms by finding the group that fit, and it is also easier to study organisms when they
are sorted in groups. When a classification name (in Latin) is written it should be
underlined, and when typed it should be in italics.
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Classification can be based on two different systems, natural and artificial. Natural
classification is based on the ideas of homologous structures and evolutionary
relationships.
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Homologous structures are features of organisms that are similar in structure, but may
differ from each other and might be used for different purposes.
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Analogues thus look the same but are different, and homologues look different but are
the same.
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Body parts are considered homologous if they have
- the same basic structure
- the same relationship to other body parts, and, as it turns out,
- develop in a similar manner in the embryo.
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The most useful way for scientists to organize biological diversity is to group organisms
according to shared evolutionary history. This way the grouping not only results in an
organized classification, it also contains and conveys information about our
understanding of the evolutionary history of these groups.
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An evolutionary relationship is where biologists group organisms together which are
structurally similar and share common ancestors.
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Early attempts of classification produced the artificial classification that was based on
grouping organisms according to:
- the way they affect people (domesticated or wild, edible or poisonous
- a superficial characteristic (can or can't fly; does or doesn't walk)
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Artificial classification systems are also used as the basis for dichotomous keys that
biologists use to identify organisms. In the Binomial System an organism is given two
Latin names, the first name is the genus and the second name is the species.
The Institute of Information Technology, 2008
SUMMARY
Module 1: Characteristics, Classification and Diversity of Living Organisms
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A dichotomous key is a series of questions asking you about features which you can see
on an organism. In each case, two descriptions are given. You have to choose which
one applies. This process is repeating itself, until you arrive at the identity of an unknown
organism.
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The 5 kingdoms are Prokaryotes, Protoctists, Fungi, Plants and Animals.
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We saw that the kingdom Prokaryotes (also known as bacteria) is unicellular (single
celled) organisms. Bacteria are classified as living organisms, because they carry
out movement, respiration, growth, sensitivity, feeding, excretion and
reproduction.
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In the Protoctist kingdom all organisms are single celled. The body of Protoctists is
one cell that contains different structures called Organelles that carry out daily
function much like our organs do. One type of organelle found in many protists is the
Chloroplast. Chloroplasts are organelles that produce food for the organism through
a process called Photosynthesis. Therefore organisms that have chloroplasts do
not ingest their food. Protoctists are aquatic. Nearly every animal, fungus and plant
has protoctist associates.
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Single-celled organisms look like animals in the way that they feed because they feed on
other tiny microorganisms such as bacteria, but they are not classified as animals.
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Kingdom fungi include organisms such as mushroom, mould, yeast and toadstool.
Fungi look like plants because they grow on substrates, but they are not plants as
they cannot make their own food by photosynthesis. Most fungi are multicellular
(with many cells) organisms, except yeast, which is a single-celled organism. Their
bodies are made up of thread-like structures called hyphae which eventually form
mycelium.
Fungi reproduce asexually by producing spore.
Fungi have no
chlorophyl with chloroplasts; therefore they do not make their own food by
photosynthesis. They use their hyphae to absorb nutrients from dead plant and
animal materials. Before they absorb nutrients, the hyphae of the fungi secrete
enzymes into food substances to digest it. This means that digestion takes place
externally. This way of nutrition is called saprotrophic nutrition.
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The Plant kingdom includes all the green plants on our earth, except algae (which is
from the kingdom protoctist). Plants are multi cellular organisms and their cells have
nuclei and cellulose cell walls. Organisms in the plants kingdom contain
chloroplasts with chlorophyll in their cells; therefore they make their own food by
photosynthesis. The Plant kingdom are divided into flowering plants (plants that bear
flowers and produce seeds) and non-flowering plants. There are two kinds of
flowering plants: monocotyledons and dicotyledons.
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Kingdom Animals include all animals, except protozoa. All animals are multi
cellular organisms. Animals obtain energy by feeding on organic materials. There
are two main groups of animals: invertebrates (organisms without a backbone) and
vertebrates (organisms with a backbone).
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Viruses are so different from other organisms that they cannot be classified as living
organisms. They are non cellular as they are not made up of cells. They do not have
organelles that are in all living cells. Viruses are made up of a single strand of either
DNA or RNA that is surrounded by a protein coat. Viruses do not have their own
metabolism and are parasitic; they do not have all of the functions that all living
organisms have, but they can reproduce when they invade a host cell. Viruses are
responsible for causing diseases in plants and animals.
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Flowering plants has roots, stems and leaves. They reproduce by producing
seeds from their flowers. Flowering plants are many-celled organisms with cells
made up of cell walls, nuclei and chloroplasts containing chlorophyll. Nutrients in soil,
The Institute of Information Technology, 2008
SUMMARY
Module 1: Characteristics, Classification and Diversity of Living Organisms
water and air are turned into food by energy that they receive from sunlight in a
process called photosynthesis.
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Flowers are the sex organs of plants.
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There are two classes of flowering plants, monocotyledons and dicotyledons.
Monocotyledonous plants usually have long, narrow leaves with parallel veins. They
contain one cotyledon inside their seeds. The flowers of a monocotyledonous plant
have petals and sepals that are indistinguishable; their roots are shallow, fibrous
and grow from the base of the stem. Flower parts are usually in groups of three or
multiples of three.
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Dicotyledonous plants have two cotyledons inside their seeds, leaves are broad with
branching or network veins, the flowers of the dicotyledonous plants’ petals and sepals
are clearly distinguishable, their petals are arranged in groups of four or five. The
root system consists out of a main root called the tap root, which grows deep into the soil
and lateral roots branch from the tap root.
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Animals are classified into two main groups Invertebrates (without a backbone) and
Vertebrates (with a backbone). There are three phyla of invertebrates that you need to
know: molluscs, annelids and arthropods.
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Molluscs have unsegmented soft bodies with slimy skin, and most molluscs have
one coiled or two uncoiled hard shells, they live on land and in water.
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Annelids are a long cylindrical invertebrate animal that have segments and a body
cavity. It includes the earthworms, leeches, and related forms. Annelids have very welldeveloped internal organs. They also have fluid inside their bodies to help them
keep their shape, as they do not have a hard exoskeleton or endoskeleton; they also
have mucus on their skin to protect them from being damaged.
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Arthropods include classes such as insects, arachnids, crustaceans and myriapods.
Arthropods are the largest phylum. All arthropods have the following features in
common: they have many jointed legs, segmented bodies and an exoskeleton
made of chitin and covered with a waterproof cuticle that protects and supports
the body. Arthropods are divided into four classes: Insects (insecta), Arachnids
(arachnida), Crustaceans (crustacean) and Myriapods (myriapoda).
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The main diagnostic features of insects are that they have one pair of antennae, one
pair of compound eyes, one or two pairs of wings, three pairs of jointed legs on the
thorax and a body that is divided into the head, thorax and abdomen.
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The main diagnostic features of arachnids are a body divided into two parts: the
cephalothoraxes (head and thorax) and abdomen, no antennae but have chelicerae
to hold the prey, several pairs of simple eyes and four pairs of jointed legs.
Arachnids are carnivores.
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The main diagnostic features of crustaceans are: Eyes in stilts, two pairs of
antennae and a body that is divided into cephalothorax and abdomen. Crustaceans
have a hard outer shell.
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The main diagnostic features of centipedes (myriapods) are: Flattened bodies
divided into segments, One pair of legs per segment, A head with a single pair of
antenna, poison claws and strong mouthparts. Centipedes are carnivorous.
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The main diagnostic features of millipedes (myriapods) are: Rounded bodies divided
into segments, Two pairs of legs per segment, A head with a single pair of antenna
and strong mouthparts. Millipeds are herbivorous.
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Cnidarians are also known as coelenterates; they are some of the simplest animals on
earth and live in water. Cnidarians have a sac-like body cavity with a single opening
at one end. The body wall consists of two layers of cells; an inner endoderm and
The Institute of Information Technology, 2008
SUMMARY
Module 1: Characteristics, Classification and Diversity of Living Organisms
an outer ectoderm. Cnidarians do not have a middle layer (mesoderm) and does
therefore not have body cavity between the two layers of cells. The body plan of a
cnidarian is described as diploblastic acoelomate.
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Nematodes are described as roundworms. They have long, round, narrow bodies
that are pointed at both ends. The body of a roundworm is not segmented and is
covered in a smooth cuticle. Nematodes have an anus and mouth. Nematodes are
colourless and unsegmented. Nematodes may be free-living, predaceous, or
parasitic. Nematodes are the most numerous multicellular animals on earth.
Nematodes possess digestive, nervous, excretory, and reproductive systems, but
lack a discrete circulatory or respiratory system.
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Vertebrates are animals with an internal skeleton made of bone. Vertebrates
belong to the phylum chordate. There are five classes of vertebrates: fish,
amphibians, reptiles, birds and mammals.
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The sub-phylum category for fish is called Pisces. All fish are aquatic, fish have a
streamlined body with scales and gills for breathing. Gills perform the gas exchange
between the water and the fish's blood. They allow the fish to breathe oxygen in the
water. Fishes are vertebrates that have a skeleton made of either bone or cartilage.
Fish can be herbivorous or carnivorous.
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The class Amphibia includes frogs, toads, salamanders and newts. They have smooth,
moist skins with no scales. Amphibians lay their eggs in water and young
amphibians tend to resemble small fish. Depending on the species of amphibian,
breathing can take place in gills, lungs, the lining of the mouth, the skin, or some
combination of these.
Amphibian's body temperature changes with its
environment. Amphibians hibernate during the winter.
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All reptiles are cold-blooded, which is why they warm themselves in the sun, and have
bodies covered in dry, horny scales. Some reptiles lay eggs; others give birth to live
young. Reptiles breathe with their lungs. Reptiles have scales that protect their
skins against dry conditions; their eggs have tough shells that prevent them from
being damaged, as most reptiles do not look after their eggs after it was laid.
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Birds are warm-blooded vertebrate animals that have wings, feathers, a beak, no
teeth, a skeleton in which many bones are fused together or are absent, and an
extremely efficient, one-way breathing system. Flying birds have strong, hollow
bones and powerful flight muscles.
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Mammals have a dry skin that is covered with hair or fur. Unlike other animals,
mammals have body hair, have 3 middle ear bones (the malleus, incus, and stapes),
and nourish their young with milk that females produce in modified sweat glands
that are called mammary glands. Mammals have sweat glands in their skin that
produce sweat to regulate body temperature.
The Institute of Information Technology, 2008