Biology IGCSE Notes

• Cell Structure: Understanding the function of organelles such as the nucleus, mitochondria, and ribosomes is essential for grasping cellular processes.

1. Classification of Living Organisms

Biology is the study of living organisms. Living organisms possess seven characteristics that differentiate them from non-living objects (MRS GREN):

1. Movement: An action causing a change of position.

2. Respiration: Chemical reactions releasing energy from nutrient molecules.

3. Sensitivity: Ability to detect and respond to stimuli.

4. Growth: Permanent increase in size and dry mass.

5. Reproduction: Process to produce more of the same organism.

6. Excretion: Removal of metabolic waste and excess substances.

7. Nutrition: Taking in materials for energy, growth, and development.

Classification is sorting living organisms into groups based on shared features in morphology (body shape) and anatomy (body structure). DNA sequencing is a powerful way to classify organisms.

• The more similar the base sequences (A, C, G, and T), the more closely related the species.

• Closely related organisms have similar amino acid sequences in proteins.

Importance of classification:

• To facilitate the study of living organisms

• To facilitate the identification of living organisms

• To reflect evolutionary relationships (common ancestor).

Classification of human beings:

• Kingdom: Animals

• Phylum: Chordates

• Class: Mammals

• Order: Primates

• Family: Hominids

• Genus: Homo

• Species: Sapiens

*Species: group of organisms that can reproduce to produce fertile offspring.

The binomial system of naming species is an internationally agreed system where the scientific name is made of 2 parts:

• The first name is the genus name (starts with a capital letter).

• The second name is the species name (starts with a small letter).

• Both names are written in italics or underlined.

The name is written in Latin.

Classifying Living Organisms into 5 Kingdoms

Living organisms are classified into 5 kingdoms: Prokaryotes, Fungi, Protoctists, Plants, and Animals.

Plants are divided into Flowering plants and Non-flowering plants (ferns).

Viruses:

• They don’t show the typical feature of living organisms (MRS GREN) unless they are inside the cells of another living organisms.

• They reproduce in the host cell causing harm to their host.

• Like living things as they have a core of DNA or RNA /have proteins/can reproduce

• Like non-living as they have no cytoplasm or organelles/don’t carry out any function except reproduction.

Animals are multicellular, have no cell walls, are heterotrophs, and most are motile.

Vertebrates have different classes:

• Amphibians

• Reptiles

• Mammals

• Fish

• Birds

Arthropods have an exoskeleton, segmented bodies, and jointed legs. Classes include Insects, Arachnids, Crustaceans, and Myriapods.

Dichotomous keys are a set of questions about an organism to identify it. The answer to each question leads to another question until the organism is identified.

2. Cell Structure and Organization

• All living organisms are made up of living cells.

• The cell is the basic unit of structure and function of all living organisms.

• The cells are very small and can only be seen under the microscope.

• New cells are produced by division of existing cells.

Plant cell:

• Cell membrane

• Cytoplasm

• Nucleus

• Cell wall made of cellulose

• Ribosomes

• Mitochondria

• Chloroplasts

• Large central vacuoles

Animal cells:

• Cell membrane

• Cytoplasm

• Nucleus

• Ribosomes

• Mitochondria

• Small vacuoles

Bacterial cells:

• Cell membrane

• Cytoplasm

• Cell wall made of murein

• Ribosomes

• Circular DNA

• Plasmids

Comparison of Animal and Plant Cells:

Mitochondria: Enclosed in two membranes, inner membrane is folded to increase surface area for aerobic respiration.

Chloroplasts: Oval structures, contain chlorophyll, essential for photosynthesis.

Cell type and its function, adaptation:

• Red blood cell

• Ciliated cell

• Neurons

• Palisade cell

• Root hair cell

3. Movement in and out

*Diffusion: The net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement.

Factors affecting the rate of diffusion:

1. Temperature

2. Concentration gradient

3. Surface area

4. Size of the molecule

5. The barrier membrane thickness

*Osmosis: It is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through partially permeable membrane.

*Active transport: It is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration.

4. Biological Molecules

Biological molecules are essential organic and inorganic molecules in living cells used to build up structures inside the cell and structures required in the cell’s metabolism.

Reducing sugar(simple sugar) e.g., Glucose:

• Benedict test give orange red or brick red precipitate.

Proteins e.g., Amylase:

• Biuret test give Purple /mauve colour

Fats or oils:

• Ethanol or emulsion test give Milky emulsion

5. Enzymes

*Catalyst: The substance that increases the rate of a chemical reaction and is not changed by the reaction.

*Enzyme: protein that function as biological catalyst.

Enzymes work by the lock and key mechanism, are proteins, catalysts, and specific. They function best at an optimum temperature and pH.

Comparison between the optimum pH of 3 digestive enzymes:

adaptation of temperature to the work of enzymes:

Current industrial uses of enzymes:

• Biological washing powder (Lipases, Proteases)

• Juice extraction (Pectinase)

• Production of lactose-free milk (Lactase)

6. Plant Nutrition

It is the process by which plants manufacture carbohydrates from raw materials using energy from light.

Raw materials:

• Carbon dioxide

• Water

• Sunlight

• Chlorophyll

Products:

• Glucose

• Oxygen

Fate of glucose:

• Converted to starch as energy store.

• Cellulose to build cell walls.

• Glucose used in respiration to provide energy.

• Converted to sucrose for transport in the phloem.

• Converted to nectar to attract insects for pollination.

External structure of a (dicot)leaf:

1. It is supported by a petiole ® to expose as much of it as possible to sunlight.

2. Has large surface area® to absorb more light and carbon dioxide to fasten rate of photosynthesis.

3. Thin ®to allow sunlight to penetrate to all cells to allow CO2 to diffuse in and O2 to diffuse out faster.

There is no all parts of photosynthetic experiment mentioned here.

Factors that affect photosynthesis:

1. Light intensity

2. Carbon dioxide.

3. Temperature

4. Chlorophyll

7. Plant Transport

Plant transport systems include:

1. Xylem

2. Phloem
   Water uptake by the plant mechanism of movement of water in the plant transpiration pull

determine how much water is lost from the leafy shoot.

Compare between xylem and phloem

Function
Feature Adaptation of Hydrophytes and Xerophytes

8. Animal Nutrition

Nutrition (feeding): taking in of materials for energy, growth and development.
Nutrients: are substances in food that the body uses: To provide energy To provide materials for making new cells and other parts of the body.*

Balanced diet: intake of nutrients in correct amounts according to age, sex, occupation.

Water is considered a nutrient and fibres (roughages) Indigestible food mostly cellulose made by plants.

Human mechanical and chemical digestive system:

*Incisions
*Canin
*Premolars
*Molars

And their structure and function in digestive system.The path of food through the alimentary canal

The role of liver and cholera in food absorption.
Functions of liver.

Test for food sample:

• Starch
  *Proteins
  *Sugar

9. Animal Transport

The components of blood, including plasma, red blood cells, white blood cells, and platelets, and their function are:

Adaptation of red blood cells:
White blood cells:
Platelets:
Functions of blood:
What causes human transport circulatory system.
Human system structure and function, arteries, vessels e.t.c, double versus single circulation with benefits and negative effects, normal heartbeat, the normal heart beats in athletes and those who exercise

Explain what cause coronary heart diseases (CHD)

10. Gas Exchange

Gas include:
Lungs, intercostal muscle and Diaphrargm. The human system importance, and its effects of physical activities on breathing rate

Gasous exchange adaption and mechanism of breathing and pathway all types.

The concentration of of: (Carbon and oxygen)

11. Respiration

the chemical reactions in cells that break down nutrient molecules and release energy for metabolism, its involve enzymes.

Aerobic and Anaerobic which including chemical reactions and uses of energy, its product. Uses of human body include :

• Formation of substance

  • Movement

  • Generation of nerve impulses

  • Cell division

  • active trasport.
    what is oxygen debt of a body while body reaction to the high rate of (c02 ph ) .
    investigate effects of temperature and the presence of effects.

12. Pathogens, Immunity, & Drugs

• Pathogen: A disease-causing microorganism.

• Host: The body inhabited by the pathogen.

• Transmissible disease: A disease where the pathogen can be passed from one host to another.

Direct and indirect body defence.

13. Excretion

The removal of the waste products of metabolism and substances in excess of requirements, its is an homeostatis for maintain balance of water. explain all human organ in excretion with their functions.

Urinary system kidney to nephron to renal. And what is kidney structure, liver and reanal veinal blood . Urea formation by damage.
describe all types of effects and factor affected by the urine.

14. Coordination

The human system consists of the:

• Central nervous system (Brain and spine ).

• Periphial nervous system. Building units of the system: system and their relationship to the spinal cord, and Synaps for the nervous transmission.

Describe : Neuron reflex, voluntary actions and effect of diseases. Types of nerves : (sensory, motor).
Desicribe the human Sence organs( eyes , nerves their functions and distribution to retina.
explain what Accommodation human body adjustment of eye lens its ciliary muscle for both bright and sunlights.

15. Inheritance

Explain ; transmission for chromosome in an , gene, DNA which carries for its alleles.

Also, , meiosis is used for nuclear for genetically for sell production to mitosis with stem . describe : what alleles traits. (Homozygous /heterozygous).
determine genetics of .test test for individuals to a recessive genotype which leads to new allile combinational variety.Sex-linked trait by sex chromosomes in male/ female to be inherited by their offspring, describe sickle cell anaemia' inheritance in tropical of Africa.(Co Dominance).

16. Variation and Selection

Describe ; the diffrence between inter.
Discontinios variation.
Continouse Variations

Pts the causes for genetics Mutation is the only. Source if and how it cause radiation. What is Adaptiva for increases.
natural/selection

Explain theory of spontaneous mutation selection

17. Reproduction in Flowering Plants

Explain sexual reproduction between its two parents . parts of the flower and what type of adaptation between for wind and insects.
transition from pollen.
what do need condotion to grow in a proper temperature 02