Biology Chapter: Plant and Animal Cells

CAIE IGCSE Biology Summary Notes

• This document is a summary of the CAIE IGCSE Biology theory syllabus, covering material updated for the 2023-2025 and 2026-2028 syllabuses.

1. Characteristics and Classification of Living Organisms

• Living organisms share characteristics summarised by the acronym MRS GREN (Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition).
• Dichotomous keys are used to classify organisms based on observable features.
• The Five Kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.
• Classifying organisms helps to show evolutionary relationships.
• DNA base sequence analysis is used to determine evolutionary relatedness.

1.1. Characteristics of Living Organisms

• Movement: Organisms move or parts of their organism change position.
• Respiration: Chemical reactions break down molecules for energy release.
• Sensitivity: Organisms detect and react to changes in their surroundings.
• Growth: Permanent increase in size and dry mass.
• Reproduction: Organisms make more of the same kind.
• Excretion: Removal of waste products and excess materials.
• Nutrition: Obtaining raw materials for energy and growth

1.2. Concept and Uses of Classification System

• Organisms are grouped based on shared characteristics.
• Species are groups of organisms that can interbreed to produce fertile offspring.
• Classification sequence is Kingdom, Phylum, Class, Order, Family, Genus, Species (King Philip Came Over For Good Soup).
• Binomial Nomenclature is a two-part naming system (Genus species) for organisms. The Genus is capitalized, and species is lowercase.

1.3. Features of Organisms

• Five kingdoms: Monera, Protista, Fungi, Plantae, Animalia.
• Kingdoms are divided into organisms with similar characteristics.
• Key examples of the characteristics of these kingdoms are provided.

1.4. Vertebrates

• Mammals (fur, mammary glands)
• Fish (scales, gills)
• Reptiles (scales, lay eggs)
• Birds (feathers, lays eggs)
• Amphibians (smooth skin, lay eggs).

1.5. Arthropods

• Invertebrates: organisms without a backbone
• All arthropods have exoskeletons, jointed legs, and segmented bodies.
• Examples of arthropod groups: Insects, Arachnids, Crustaceans, and Myriapods.

1.6. Classification of Plants

• Ferns: Do not produce flowers or seeds, reproduce by spores.
• Flowering Plants: Produce flowers and seeds, reproduce via flowers.

1.7. Viruses

• Not considered living things.
• Contain genetic material (DNA or RNA) inside protein coat.
• Reproduce inside host cells using host cell's mechanisms.

2. Organisation of the Organism

2.1. Cell Structure

• All organisms are made of cells.
• Key cell organelles include cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes.
• Eukaryotic cells contain a true nucleus and membrane-bound organelles.
• Prokaryotic cells do not contain a true nucleus or membrane-bound organelles.

3. Movement In and Out of Cells

3.1. Diffusion

• Net movement of molecules from a region of high concentration to one of low concentration.
• Influenced by concentration gradient, temperature, surface area to volume ratio, and distance.

3.2. Osmosis

• Net movement of water molecules from a region of high water potential to a region of low water potential across a partially permeable membrane.

3.3. Active Transport

• Movement of molecules against a concentration gradient, requiring energy (from respiration).
• Achieved through carrier proteins embedded in the cell membrane.

4. Biological Molecules

4.1. Biological Molecules

• Carbohydrates (CHO): Used for energy and building materials.
• Fats/Oils (CHO): Energy storage and insulation
• Proteins (CHONS): Structural components, hormones, enzymes.

4.2. Food Tests

• Tests for presence of following; Starch, Reducing Sugars, Fats, Proteins.
• Specific test procedures & colour changes indicative of each substance's presence should be known.

4.3. Structure of DNA

• DNA Structure: Double helix with two strands held together by complementary base pairing (Adenine-Thymine, Cytosine-Guanine).

5. Enzymes

• Catalysts, speeding up chemical reactions by lowering activation energy.
• Importance of Temperature & pH in enzyme activity.
• Lock & Key Model – relationship between enzyme and substrate.

6. Plant Nutrition

6.1. Photosynthesis

• Photosynthesis Equation: 6CO2 + 6H2O → C6H12O6 + 6O2
• The process whereby plants use light energy to convert carbon dioxide and water into glucose and oxygen.

###6.2. Investigation of Chlorophyll

• Experimental procedures (using variegated leaves) to demonstrate the role of light in photosynthesis.

6.3. Investigation of Light

• Experimental procedures (using variegated leaves) to demonstrate the role of light in photosynthesis.

6.4. Investigation of Carbon Dioxide

• Experimental procedures to investigate the role of carbon dioxide concentration in affecting photosynthesis rate.

6.5. Limiting Factors

• Factors (light intensity, carbon dioxide concentration, and temperature) that can constrain photosynthesis.

6.6. Leaf Structure

• Adaptations (cuticle, stomata, vascular bundles) that optimize photosynthesis and water conservation.

7. Human Nutrition

7. 1. Diet

• Balanced Diet: A diet containing carbohydrates, fats, proteins, vitamins, minerals, and water in suitable proportions for good health.

7.2. Nutrition

• Importance of specific nutrients (glucose, proteins, fats, vitamins).
• Different nutrients' roles and functions should be known.

7.3. Deficiencies

• Deficiency diseases related to Vitamin C, Vitamin D, Ca, Fe.
• Specific symptoms associated with each deficiency should be understood.

7.4. Digestive System

• Key organs (mouth, oesophagus, stomach, duodenum, ileum, large intestine, rectum, anus). Also, the role of associated organs (liver, pancreas)
• Mechanical and Chemical Digestion & Absorption and Assimilation - the steps in the digestive process - The main roles of enzymes (Amylase, Protease, Lipase) and bile.

7.5. Teeth

• Different types of teeth (incisors, canines, premolars, molars).
• Structure and function of each tooth type in chewing should be known.

8. Transport in Plants

8.1. Xylem and Phloem

• Xylem: Transports water and dissolved minerals from the roots to the leaves.
• Phloem: Transports sucrose and amino acids from source to sink.
• Adaptations of xylem and phloem cells for their function.

8.2. Water Uptake

• Root hair cells take up water from the soil by osmosis.
• Water moves from roots to the leaves through the xylem.

8.3. Transpiration

• Evaporation of water from leaves through stomata.
• Factors that affect transpiration rate (e.g., temperature, humidity, wind, light).

9. Transport in Animals

9.1. Circulatory Systems

• Components of the circulatory system (heart, blood vessels, blood).
• Single vs. double circulatory systems. Understanding the differences in the structures of these systems, and their adaptations, is essential.

9.2. Heart

• Structure of the mammalian heart (atria, ventricles, valves, coronary arteries).

9.3. Functioning of the Heart

• Pathway of blood through the heart in both systemic and pulmonary circuits.

9.4. Exercise on Heart Rate

• Effects of exercise on the heart rate and ECG.

9.5. Coronary Heart Disease

• Causes and prevention of coronary heart disease.

9.6. Blood Vessels

• Structure and function of arteries, veins, and capillaries.

9.7. Blood

• Components of blood (plasma, red blood cells, white blood cells, platelets).
• Functions of each blood component in circulatory system

10. Diseases and Immunity

10.1. Pathogens

• Organisms that cause disease (types, modes of transmission).
• Examples of Diseases caused by pathogens

10.2. Body Defences

• Barriers to infection: skin, mucus, cilia.
• Mechanisms of action of phagocytes and lymphocytes (e.g., via anti-bodies), including the role of specific antibodies.
• Vaccination: how vaccination builds immunity -Passive Immunity: short-term immunity acquired via antibodies from another individual -Active Immunity: long-term immunity acquired via the body developing antibodies from exposure to a pathogen Different types of pathogens, and ways they can be transmitted

11. Gas Exchange in Humans

11.1. Gas Exchange Surfaces

• Structure and function of gas exchange surfaces (e.g., alveoli).
• Properties of efficient gas exchange surfaces, (thin surface/large surface area/good ventilation/good blood supply)

11.2. Structure of the Lungs

• Structure of the respiratory system (diaphragm, intercostal muscles, trachea, bronchi, bronchioles, alveoli).

11.3. Physical Activity on Breathing

• Factors influencing breathing rate and depth during exercise

11.4. Breathing

• Mechanisms of breathing (inspiration and expiration).
• Muscle action - diaphragm and intercostal muscles.

12. Respiration

12.1. Respiration

• Aerobic Respiration: complete breakdown of respiratory substances (glucose) using oxygen to produce energy (ATP).
• Cellular Respiration & its many uses for the body, for example, muscle contraction, protein synthesis, and maintenance of the body temperature
• Anaerobic Respiration: incomplete breakdown of respiratory substances (glucose) without oxygen to produce energy (ATP) as a less efficient process

12.2. Aerobic Respiration

• Details of the equation and products

12.3. Anaerobic Respiration

• Details of the equation and products, and conditions under which it occurs (e.g., intense exercise)

13. Excretion in Humans

13.1. Excretion

• Removal of waste products and excess materials from the body.
• The organs involved in the process of excretion
• The importance of excretory products (e.g., urea, excess water and salts).

13.2. Function of Liver

• Role of liver in deamination of amino acids, breakdown of urea formation, filtering toxins, and role in carbohydrate and fat metabolism.
• Bile's role in digestion.

13.3. Function of Kidney

• Kidney structure (cortex, medulla, pelvis)
• Process of urine formation (filtration, reabsorption, secretion).
• Role of kidney in regulating water balance & blood composition

14. Coordination and Response

14.1. Mammalian Nervous System

• Central Nervous System (brain and spinal cord)
• Peripheral Nervous System - (nerves and neurons)
• Body functions regulation
• Types of Neurones
• Sensory: transmit messages from receptors to central nervous system
• Relay: connect sensory and motor neurons in the central nervous system
• Motor: transmit messages from central nervous system to effectors
• Electrical impulses

14.2. Types of Neurones

• Different types of neurons and their functions within the nervous system (structure, function)

14.3. Simple Reflex Arc

• Relay neurons: Connect sensory to motor neurons in the central nervous system.
• How it represents a reflex action
• The different components of the reflex arc and their function

14.4. Synapse

• Structure/Function of Synapses
• Neurotransmitters: transmit signals across the synapse

14.5. Sense Organs

• Groups of receptors (cells/organs) detecting specific types of stimuli (e.g., light, sound, temperature).

14.6. Pupil Reflex

• Involuntary responses to light intensity within the eye

14.7. Accommodation

• Adjusting the lens to focus on near and distant objects.

14.8. Rods and Cones

• Types of photoreceptor cells in the retina, and their roles related to visual acuity and night vision.

14.9. Hormones

• Mechanism of hormonal action, roles of hormones and how they are produced/used (Adrenaline, Insulin, testosterone, estrogen, glucagon)
• Key chemical messages produced and used by various endocrine glands

14.10. Nervous and Hormonal Control

• Comparison of nervous and hormonal control systems in terms of speed of action, transmission route and area of response.

14.11. Homeostasis

• Dynamic equilibrium and the concept of regulation.
• Negative Feedback Mechanisms

14.12. Homeostasis: Blood Glucose Control

• Regulation of blood glucose concentration
• The roles of insulin and glucagon in maintaining homeostasis, and how they work in a feedback loop to maintain the glucose level.

14.13. Homeostasis: Temperature Regulation

• Mechanisms that help maintain body temperature.

14.14. Tropic Responses

• Roles of Plant Hormones (Auxins) in controlling plant responses, such as phototropism and gravitropism.

16. Reproduction

16.1. Asexual Reproduction

• Types and processes of asexual reproduction (e.g. binary fission, budding).
• Advantages/Disadvantages

16.2. Sexual Reproduction

• Process and advantages/disadvantages of sexual reproduction.
• Fertilisation stages
• Haploid/Diploid concepts

16.3. Sexual Reproduction in Plants

• Flower structure - Male and female parts
• Pollination (Insect and Wind)

16.4. Pollination

• Agents of pollination - how each method works

16.5. Germination

• Role of water, oxygen, and temperature in germination.

16.6. Sexual Reproduction In Humans

• Structure of the Male and Female reproductive systems.
• Gamete production (Sperm/Ovum) and their adaptations – fertilisation in humans and development, and the process of the menstrual cycle

17. Inheritance, Genes and Proteins

17.1. Chromosomes, Genes and Proteins

• The structure and role of DNA and how it codes for proteins
• Coding for DNA segments (gene → protein link.)

17.2. DNA and Protein Synthesis

• Transcription and translation in terms of the sequence of bases for a gene and how proteins are made

17.3. Cell Division: Mitosis

• Stages and purpose of mitosis in asexual reproduction and growth.
• Chromosome number maintenance

17.4. Cell Division: Meiosis

• Purpose and stages of meiosis in sexual reproduction (gamete formation)
• Reduction of chromosome number

17.5. Monohybrid Inheritance

• Understanding the terms related to monohybrid inheritance (e.g., genotype, phenotype, homozygous, heterozygous, dominant, recessive alleles).

18. Variation and Selection

18.1. Variation

• Causes and types of variation (continuous and discontinuous variation)

18.2. Adaptive Features

• Factors affecting population size
• Adaptive features related to survival, such as adaptations to extreme temperatures/water availability and other environmental conditions.

18.3. Selection

• Natural Selection and how it operates.
• Examples of natural selection.
• Artificial Selection

19. Organisms and their Environment

19.1. Energy Flow

• Food Chains & Pyramids and Food Webs
• Efficiency of energy transfer within food chains and webs.
• Energy is lost at each stage/level of a food chain through respiration.

19.2. Nutrient Cycles

• Summary of Carbon and Nitrogen cycles, and their importance

19.3. Population

• Population factors (growth, size, carrying capacity)
• Factors influencing population size: food supply, predation, disease.

19.4. Sigmoid Curve of Population Growth

• The concept of population growth curves and factors affecting growth rate.

20. Human Influences on Ecosystems

20.1. Food Supply

• Factors (mechanisation, fertilisers, pesticides, herbicides, and monoculture) that influence food production.

20.2. Habitat Destruction

• Impacts of human activities on biodiversity, and reasons for habitat loss.

20.3. Pollution

• Factors that affect the quantity of pollution
• Problems associated with over-reliance on non-renewable energy sources or over-use of products that have a negative environmental impact, e.g., pesticides, and waste disposal etc.

20.4. Conservation

• Importance of sustainable resource use
• Conservation strategies (e.g. protected areas, quotas, replanting.)

21. Biotechnology and Genetic Modification

21.1. Introduction

• Role of microorganisms in biotechnology
• Genetic Modification

21.2. Biotechnology

• Methods of using microorganisms in Biotechnology (e.g., producing biofuels, and food items.)

21.3. Fermenters

• Large-scale production vessels used in biotechnology

21.4. Genetic Modification

• Methods and examples of genetic modification.
• Genetic Engineering - changing the genetic material of an organism

21.5. Genetically Modified Crops

• Arguments for and against the use of genetically modified crops in modern food production.