Biology S6 - Rwanda Education Board

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Biology S6Student BookExperimental versionKigali August 2018

Copyright 2018 Rwanda Education BoardAll rights reserved.This document is the property of Rwanda Education Board.Credit should be given to REB when the source of this book is quotedii

TABLE OF CONTENTTABLE OF CONTENT . iiiUNIT 1 POPULATION AND NATURAL RESOURCES . 11.1 Population characteristics . 21.2 Population density: Dependent and independent factors affecting population density . 51.3Methods or techniques of measuring population density . 71.4 Population growth patterns and environmental resistance. 101.5 Natural resources and their importance . 131.6 Methods of conserving natural resources . 15End of unit assessment 1 . 18UNIT 2 CONCEPT OF ECOSYSTEM . 212.1 Ecosystem definition and types of ecosystem . 232.2 Properties of an ecosystem and ecological factors influencing the life of organisms . 272.3. Energy flow in an ecosystem . 302.4 Ecological succession . 352.5 Bioaccumulation and Bio magnification . 382.6 Efficiency of ecological production . 412.7 Biogeochemical Cycles . 45End of unit assessment 2 . 50UNIT 3 EFFECT OF HUMAN ACTIVITIES ON ECOSYSTEM . 533.1 Modern agricultural technologies for food production . 543.2 Impacts of human activities on ecosystem. 563.3 Pollution . 613.4 Biological conservation and restoration. 65End of unit assessment 3 . 68UNIT 4 THE CIRCULATORY SYSTEM . 684.1 Blood circulatory system in animals . 704.2 Structure of the human heart . 764.3 Heart beat and mammalian cardiac cycle . 774.4 Control of the heart rate. . 824.5 Blood vessels . 84iii

4.6 Body fluids, composition and functions . 864.7 Transport of respiratory gases . 924.8 Blood clotting and common cardiovascular diseases . 954.9 Lymphatic system . 98End of unit assessment 4 . 102UNIT 5 ENERGY FROM RESPIRATION . 1055.1 Need for energy by organisms . 1065.2 Structure of Adenosine Triphosphate and its importance . 1075.3 Synthesis and breakdown of ATP . 1095.4 Respiratory substrates and their relative energy values . 1115.5 Measurement of respiration and respiratory quotient . 113End of unit assessment 5 . 118UNIT 6 CELLULAR RESPIRATION . 1216.1 Overview of respiration process . 1216.2 Link reaction and the Krebs cycle . 1246.3 Oxidative phosphorylation and electron transport chain . 1266.4 Efficiency of aerobic and anaerobic respiration . 1286.5 Factors affecting the rate of respiration . 1316.6 Use of other substrates in respiration . 133End of unit assessment 6 . 135UNIT 7 EXCRETION AND OSMOREGULATION . 1377.1 Structure and functions of excretory organs in mammals . 1387.2 Structure and the functions of the nephron. . 1427.3 Formation of urine and purification of blood . 1467.4 Role of hypothalamus, pituitary gland, adrenal gland and nephron in varying the bloodosmotic pressure. 1487.5 Kidney transplants and dialysis machines . 1507.6 Principles of osmoregulation in marine, freshwater and terrestrial organisms. . 1527.7 Excretion and osmoregulation in protoctista, insects, fish, amphibians and birds. . 1537.8 Excretion in plants . 156End of unit assessment 7 . 158iv

UNIT 8 GENERAL PRINCIPLES OF RECEPTION AND RESPONSE IN ANIMALS. . 1608.1 Types of sensory receptors and stimuli . 1618.2 Components of the sensory system: transduction, transmission and processing . 1638.3 Structure and functioning of the eye . 1658.4 Structure and functioning of the ear. 1758.5 Structure and functioning of the tongue. 1808.6 Structure and functioning of the skin . 182End of unit assessment 8 . 185UNIT 9 NERVOUS COORDINATION . 1879.1 Overview of control and co-ordination in mammals . 1879.2 Structure, types and functions of neurons . 1929.3 Nature and generation of a nerve impulse . 1969.4 Transmission of nerve impulses. 2019.5 Structure and function of a cholinergic synapse. . 2079.6 Functions of sensory, relay and motor neurons in a reflex arc . 211End of unit assessment 9 . 214UNIT 10 HORMONAL COORDINATION IN ANIMALS . 21910.1 Structure and function of the endocrine system in humans . 21910.2 Principles of the negative feedback mechanism of hormonal action. . 22710.3 Effects of hormonal imbalances. 22910.4 Comparison of hormonal and nervous systems . 232End of unit assessment 10 . 234UNIT 11 SKELETONS, MUSCLES AND MOVEMENT . 23611.1 Types of animal skeletons: hydrostatic, exoskeleton and endoskeleton. . 23711.2 Types of joints. 24911.3 Types of muscles: cardiac, smooth and skeletal muscle . 25311.4 Ultrastructure and functioning of striated muscle . 26411.5 Sliding filament theory of muscle contraction . 266End of unit assessment 11 . 268UNIT 12 HUMAN REPRODUCTION . 26912.1 Menstrual cycle . 270v

12.2 Oestrous cycle . 27312.3 Copulation, fertilization and embryo development. . 27312.4 Role of Placenta in the development of embryo . 27812.5 Physiological changes during pregnancy and parental care . 28012.6 Twins and multiple births . 28312.7 Infertility or barrenness . 28512.8 Family planning: birth control and contraception . 28712.9 Causes and prevention of STIs and HIV. 289End of unit assessment 12 . 293UNIT 13 PRINCIPLES OF GENE TECHNOLOGY . 29513.1 Recombinant DNA and enzymes involved in genetic engineering . 29613.2 Properties of plasmids and gene manipulation . 30113.3 Transfer of genes using plasmids in transgenic organisms . 30313.4 Non-biological methods of gene transfer . 31013.5 Principles of Polymerase Chain Reaction (PCR) in cloning and amplifying DNA . 32013.6 Gel electrophoresis. 32313.7 Use of microarrays in the analysis of genomes and in detecting mRNA . 327End of unit assessment 13 . 331UNIT 14 APPLICATION OF GENE TECHNOLOGY . 33314.1 Bioinformatics. 33514.2 Production of human proteins by recombinant DNA technology . 33614.3 Genetic technology applied to medicine and forensic science . 33814.4 Significance of genetic engineering in improving the quality and yield of crop plants andlivestock . 34314.5 Ethical and social implications of using genetically modified organisms (GMOs). . 346End of unit assessment 14 . 349UNIT 15: VARIATION . 35215.1 Variation . 35315.2 Types of variation . 35515.3 Causes of variation in living things . 36315.4 t-test. 366vi

End unit assessment 15. 370UNIT 16 NATURAL AND ARTIFICIAL SELECTION . 37216.1 Natural selection . 37316.2 Artificial selection . 37816.3 Allele frequency and its causes . 38116.4 Study of population genetic variation by Hardy-Weinberg principle . 385End of unit assessment 16 . 388UNIT 17 EVOLUTION AND SPECIATION . 38917.1 Theories of evolution . 39117.2Evidence of evolution . 39617.3 Causes of evolution . 40017.4 Speciation . 40317.5 Roles natural selection in speciation . 40517.6 Mechanism of speciation . 406End unit assessment 17. 411REFERENCES . 413vii

UNIT 1 POPULATION AND NATURAL RESOURCESKey Unit CompetenceTo be able to describe the factors affecting population size and the importance of natural resourcesLearning ObjectivesBy the end of this unit, I should be able to:-State and define population characteristics.Explain factors that affect population density.Explain population growth patterns.Explain the terms renewable and non-renewable resources.Explain how environmental resistance affects the balance of nature.Explain the importance of natural resources in growth of the Rwandan economy and methodsof conservation.Demonstrate methods used in estimating populations by using quadrats and line transects.Research how the human population has grown over the past 250 years.Compare statistics on the population age-sex structure of developing and developedcountries.Analyse the costs and benefits of managing renewable and non-renewable resources.Support that human population explosion impacts negatively on the environment.Recognize that some resources are renewable and others are non-renewable and that effectiveuse of these resources is of great value.Justify the practice of family planning as a tool for reducing population explosion.Introductory activity1) The following pictures were taken from different areas and consist of a group ofanimals. Analyse them and answer the questions that follow.a) List down similarities and differences for pictures A and B?b) What can you conclude about the picture A and the picture B using appropriateecological terms?c) Specify the appropriate ecological term to describe picture A and picture B2) Explain briefly the characteristics of a population.3) Categorize the natural resources1

Pictures A and B represent ecological populations. In biology, an ecological population is a groupof organisms of the same species that live in the same area at a certain period of time. Thepopulation is the unit of natural selection and evolution. How large population is and how fast it isgrowing are often used as measures of its health.1.1 Population characteristicsActivity 1.1Discuss the following terms in relation to population:1) Density2) Age structure3) Growth patte

1 UNIT 1 POPULATION AND NATURAL RESOURCES Key Unit Competence To be able to describe the factors affectin