Slide 1

IGCSE O.L Biology

Prepared byMr. Walid Abou-Elyousr

Chapter (1) A. Characteristics of living organisms.

B. Classification of living organisms.

C. Diversity of living organisms.

Biology

Biology

Biology is the study of life (bios=life , logos=knowledge)

In practice , biology means study of living things.

A . Characteristics of living organisms They are certain features ,which distinguish living organisms from non-living things.1-Nutrition

It is the obtaining of organic substances and ions which the organisms can use to obtain its

a) Energy b) materials for growth

c)tissue repair.

2-Respiration

It is the break down of food ,inside the body cells by chemical reactions to produce energy.

There are two types of respiration

a)Aerobic: occurs in the presence of oxygen.

b)Anaerobic: occurs in the absence of oxygen.

3-Excretion

It is the removal of metabolic wastes / toxic substances and substances in excess of requirements from organisms

e.g. removal of carbon dioxide by the lungs and removal of oxygen by the plants during the day time.

4-Reproduction

It is the ability of the living organisms to produce new offsprings of their own kind to keep their species.

5-Sensitivty

It is the process by which the living organisms can detect and response to a stimulus.

a)Stimulus; any change in the organism's environment.

b)Response: It is the reaction of an organism to the stimuluse.g. the removal of a hand away from a hot object.

6-Growth

It is an irreversible increase in the size and dry mass by an increase in cell number or cell size or both.

7-Movement or locomotion

It is the change in the position or direction or both of the organism's body.OrAn action by an organism or part of an organism causing a change of position or place.

N.B. animals has ability to move from one place to another (total movement)

While the movement in plants is positional movement only as movements of someplants towards light or gravity.

Classification of living organisms

-Taxonomy : Is the science that deals with classification of living organisms

-Concept of classification The living organisms are classified according to the common featuers present between the members of the same group. OrLiving organisms can be sorted into groups on the bases of shared features.

-Importance of classification

1-To facilitate the study of living organisms.2-To facilitate the identification of living organisms.

Organisms are classified into groups, the largest group is known as kingdom for example plant kingdom and animal kingdom.Each kingdom is divided into smaller groups each is known as phylum .Each phylum is divided into smaller groups each is known as class which is divided into smaller groups each is known as order .Order in turn divided into groups each is known as family.Each family is divided into smaller groups each is known as genus which divided into smaller groups each is known as species . Classifictory system : series of classification:

Kingdom phylum class order family genus species. Species : It is a group of organisms which have a lot of features in common and can breed with each other producing young fertile offspring.

First nameSecond name1-Name of the genus , it is known as generic name.2-starts with a capital letter,1-Name of the species , it is known as trivial name.2-starts with a small letter. Binomial system of naming species

In this system each organism has a scientific name which consists of two words .

-The name is written LATIN in italics,or underlined.

Example: The binomial of man is Homo sapiens

(name of genus) (name of species) CLADISTICS

-There are many systems for classyfing living organisms , one of these systems is to classify living organisms to clades

-This type of classification depends on the similarity in the structure of the nucleic acids DNA and RNA .

Diversity of living organisms

Living organisms are classified into 5 kingdomsLiving organisms

Kingdom : Prokaryotes (monera) e.g. Bacteria

Kingdom : Protoctista e.g. Amoeba

Kingdom : Fungi e.g. Bread mold Mushroom

Kingdom : Plantae e.g. Onion Bean

Kingdom : Bird e.g. Bird 1-Animal kingdom

It includes two main groups A- Invertebrates B- Vertebrates A-Invertebrates 1) Phylum Arthropods

They are invertebrates animals which havea)Paired joined walking legs (for movement).

b)segmented body for flexibility.c)Hard exoskeleton which is made of chitin

- Acts as water proof reducing water loss. -Supports and protects the animal. -Provides points for muscle attachment. d) They may have compound or simle eyes. e)They are classified into 4 classes:1-Insects2-Crustaeans3-Arachnids4-Myriapods1-Insects* Examples

House fly , honey bee ,butter fly and ants.

-The body is divided into head ,thorax ,and abdomen.

-Have three pairs of jointed legs.

-Have one pair of antenna.

-Have compounds eyes (few types have simple eyes).

-Most of them have wings.

Adaptation of insects:

1-Have compound eyes for wide vision.(a compound eye is an eye composed of many units and lenses).

2-Have antenna for sensation.

3-Are small to hide from enemies.

4-Have different colors for camouflage.

5-Have jointed legs for rapid movement.

6-Have segmented bodies to facilitate their movement.

7-Have exoskeleton for protection and support.

8-Have chitineous skeleton for protection and water proof.

9-Have wings to fly.

2- Arachnids

The main characteristics

1-the body is divided into two parts only which are a) cephalothorax (head and thorax fused together). b)abdomen.

2-Have four pairs of jointed legs originated from cephalothorax.

3-Usually the legs end with claws for catching preys.

4-Have no wings.

5-Have simple eyes.

6-Have no antenna but a pair of chelicerae or pedipalps which are used to hold the prey.

Adaptation of arachnids

1Have jointed legs for rapid movement.

2-Have segmented body to facilitate their movement.

3-Have exoskeleton for protection.

Examples Spiders and scorpions

Notice that arachnids have mouth parts seen as antenna, but their function is to catch the prey, they are not known as antenna as they are not used in sensation.

3-crutaceans

The main characteristics

1-The body is divided into two parts only a) cephalothorax b) abdomen

2-Have two pairs of antenna .

3-Have one pair of stalked compound eyes

4-Most of them are aquatic respire by gills.

5-Usually have more than four pairs of legs (or appendages).

6-have no wings.

Adaptation of crustaceans

1-Have antenna for sensation.

2-Have stalked compound eyes for wide field of vision.

3-May have gills for breathing in water.

Examples

Crabs, lobsters and shrimps.

4-Myriapods

Examples : Millipedes and Centipedes

The main characteristics1-Are arthropods (have exoskeleton, segmented body and pairs of jointed legs).

2-Have head, but the body cannot obviously divided into thorax and abdomen).

3-Have a pair of legs at each body segment.

4-In millipedes the abdominal segments are fused in pairs so it seems as if it has two pairs of legs at each segment.

5-As a myriapod grows additional segments are formed.

P.O.CInsects Crustaceans Arachnids MyriapodaBody divisionsHead thorax and abdomen (3)Cephalothorax and abdomen (2)Cephalothorax and abdomen (2)Head and body (not divided into thorax and abdomenAntenna 1 pair2 pairsAbsent 1 pairEyes Compound 1 pair ,some may have simpleCompound stalked eyesSimple 8 in numberSimple 2 clusters of simple eyesWingsMay have 1or 2 pairsAbsent Absent Absent Paired legs3 pairs on the thoraxMore than 4 pair on the cephalothorax4 pairs on the cephalothorax1 or 2 pairs on each body segmentExoskel- etonMade of chitinCalcified chitin exoskeletonMade of chitinMade of chitinHabitat Mainly terrestrialMainly aquaticsTerrestrial Mainly terrestriale.g.AntsHouse fly mosquitoesCrab Lobster Shrimp Spider Scorpion Centipedes milipedes Phylum : Annelida

Examples : Earthworms

The main characteristics

1-Annelids are invertebrate worms, most of them have elongated , cylindrical bodies which are divided into segments.

2-In most annelides each segment carries a number of bristles called chaetae which help in locomotion.(no legs)

3-Most of them live in water.

4-they have reproductive structure called clitellum .

5-Have mouth and anus

NoticeThey are not considered as arthropods because they have no jointed legs.

Phylum :Nematoda

Examples Ascaris (acts as parasite in human and pigs).

The main characteristics1-Thread like unsegmented body with no rings and no legs or chaeta. 2-Elongated round invertebrate worms with pointed ends.

3-Have alimentary canal with mouth and anus.

4-Have separate sexes.

5-No obvious head.

Phylum : Mollusca

Examples Snails , oysters ,squids, octopuses ,mussels and slugs

The main characteristics

1-they are invertebrates

2-Body shape a)they are soft no segmented b)many have shell which may be coiled, tubular or consists of 2 halves (bivalve) ,some molluscs have no shell e.g. octopus.

3-All molluscs have muscular foot.

4-Some molluscs have antenna .

5-Mainly are aquatic , few lived on land.

6-Many such as snails respire by simple lungs,Squids and octopuses have gills.