1 of 32

Section I�Characteristics and Classification of Living Organisms

iGCSE

Biology

2 of 32

Learning Outcomes�Characteristics

  • To be able to list and describe the characteristics of living organisms
  • To define the terms
    • Nutrition
    • Excretion
    • Respiration
    • Sensitivity
    • Reproduction
    • Growth
    • movement

3 of 32

Learning Outcomes�Classification

  • To be able to define and describe the binomial system of naming species
  • To be able to classify the five main classes of vertebrates
  • To be able to list the main features used in the classification of flowering plants, arthropods, annelids, nematodes and molluscs
  • To be able to list the main features used in the classification of viruses, bacteria and fungi, and their adaptation to the environment.

4 of 32

Learning Outcomes�Using Simple Keys

  • To be able to use simple dichotomous keys based on easily identifiable features.

5 of 32

Characteristics of living organisms

iGCSE Biology

Section I

Characteristics and Classification of Living Organisms

6 of 32

Introduction to Living Things

7 of 32

What is Life?

8 of 32

Aliens land on Earth and watch things carefully to tell whether they are alive or not.

Would an alien think this car is alive?

9 of 32

Why aren’t fluffy toys alive?

​

Fluffy toys often look like real animals

10 of 32

Life Processes

  • If something is alive it will carry out all of the seven life processes.
    • Movement
    • Respiration
    • Sensitivity
    • Growth
    • Reproduction
    • Excretion
    • Nutrition

11 of 32

Characteristics of Living Things

  • M is for movement
    • Animals move to find food, shelter or a mate.
    • Plants do not move in the same way as animals but move towards sunlight.

12 of 32

Characteristics of Living Things

  • R is for reproduction
    • Animals lay eggs or have babies.
    • Seeds from plants grow into new plants.

13 of 32

Characteristics of Living Things

  • S is for sensitivity.
    • Animals find their way using their sense organs such as the eyes or skin.
    • Plants don’t have sense organs but do respond to gravity and light.

14 of 32

Characteristics of Living Things

  • G is for growth
    • Growth is an increase in size
    • Animals stop growing when they reach adult size.
    • Plants grow throughout their lives.

15 of 32

Characteristics of Living Things

  • R is for respiration
    • Respiration is the release of energy from food.
    • This usually needs oxygen.

16 of 32

Characteristics of Living Things

  • E is for excretion
    • All living things produce waste.
    • The removal of this waste is called excretion.
    • Animals excrete through their lungs, kidneys and skin.
    • Plants shed their leaves in autumn

17 of 32

Characteristics of Living Things

  • N is for nutrition
    • All living things need food for energy, growth and repair.
    • Animals have to find their own food and eat plants and other animals.
    • Plants make their own food by the process of photosynthesis.

​

18 of 32

Classification

19 of 32

Classification

  • Classification makes the identification of living organisms easier
  • Organisms are sorted into groups according to features they have in common.
  • The biggest group is kingdom

20 of 32

The five kingdoms

  • Bacteria
    • Very small and single-celled, no nucleus
  • Protoctists
    • Single celled, with a nucleus
  • Fungi
    • Cell walls contain chitin, with a nucleus
  • Plants
    • Multicellular organisms
    • Can make food through photosynthesis
  • Animals
    • Multicellular
    • Have to obtain food

21 of 32

Classification

  • The basic unit of classification is the species.
    • A species is a group of organisms that can breed together to produce fertile offspring.

​

  • Naming Species
    • In the Binomial system organisms are identified by two names
      • Genus and species
      • Genus always has a capital letter
    • Examples
      • Canis lupus – the wolf
      • Panthera leo – the lion

22 of 32

Classification of Invertebrates

  • The main groups of invertebrates are
    • Arthropods
    • Annelids
    • Nematodes
    • Molluscs

​

  • Here are some examples

23 of 32

Arthropods

  • Special features
    • They are invertebrates
    • They have a waterproof exoskeleton
    • Their bodies are segmented
    • They have jointed limbs

​

  • Four main classes of arthropod
    • Insects
    • Arachnids
    • Crustaceans
    • Myriapods

24 of 32

Insects

  • Examples
    • Dragon fly
    • Locust

​

  • Key features
    • Three pairs of legs
    • Two pairs of wings
    • One pair antennae
    • Compound eyes
    • Body – head, thorax and abdomen

25 of 32

Arachnids

  • Examples
    • Spider
    • Tick

​

  • Key features
    • Four pairs of legs
    • Body divided into head and abdomen
    • Several pairs simple eyes
    • Chelicerae for biting / poisoning prey

26 of 32

Crustaceans

  • Examples
    • Crab
    • Woodlouse
  • Key features
    • Five or more pairs of legs
    • Two pairs of antennae
    • Head and abdomen
    • Exoskeleton forms a hard carapace
    • Compound eyes

27 of 32

Classification of viruses, bacteria and fungi

28 of 32

Viruses, e.g. HIV

  • Very small
  • NOT cells
  • Contain a strand of DNA or RNA
  • Surrounded by a protein coat (capsid)
  • Only life process they show is reproduction (inside host cells)

29 of 32

Bacteria e.g. E. coli

  • Small
  • Cell wall, cell membrane and cytoplasm
  • No nucleus, DNA is a single coil
  • Some have a slime capsule
  • Some have flagellae (for movement)

30 of 32

Fungi e.g. Mucor

  • Multicellular fungi are composed of hyphae
  • Cell walls made of cellulose or chitin
  • Do not photosynthesis
  • Some produce spores

31 of 32

Classification of Plants

32 of 32

Classification of flowering plants

  • Key features
    • Multicellular organisms
    • Cellulose cell walls and sap vacuoles
    • Roots, stems and leaves
    • Some cells contain chloroplasts
    • Two groups
      • Monocotyledons
      • Dicotyledons
      • The term cotyledon means “seed leaf”