6.2.3

Natural Selection

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Natural Selection

Natural selection was proposed by Charles Darwin in 1859. He theorised that all species evolved from simple life forms that first appeared on Earth more than three billion years ago. Natural selection happens like this:

Genetic variation

Genetic variation

  • Within a biological population, different individuals have genetic variation (differences in characteristics).
Survival of the fittest

Survival of the fittest

  • Individuals possessing genes that make them better adapted to the environment will have a greater chance of survival.
Breeding

Breeding

  • Individuals with the best chances of survival are the most likely to breed successfully (because they survive).
Best characteristics survive

Best characteristics survive

  • The characteristics responsible for the increase in the likelihood of survival are more likely to be passed on to the next generation.
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1

Cell Biology

1.1

What's in Cells?

1.1.1Types of Cells1.1.2Properties of Prokaryotes1.1.3Orders of Magnitude1.1.4Standard Form1.1.5Standard Form - Calculations1.1.6Addition in Standard Form - Calculations1.1.7Subtraction in Standard Form - Calculations1.1.8Multiplication in Standard Form - Calculations1.1.9Division in Standard Form - Calculations1.1.10Animal Cells1.1.11Plant Cells1.1.12Differentiation in Plants & Animals1.1.13Bacterial Cells1.1.14Types of Cells HyperLearning1.1.15Cell Specialisation in Animals1.1.16Sperm Cells1.1.17Nerve Cells1.1.18Muscle Cells1.1.19Cell Specialisation in Plants - Root Hair Cells1.1.20Cell Specialisation in Plants - Xylem1.1.21Cell Specialisation in Plants - Phloem1.1.22Microscopy1.1.23Magnification1.1.24Developments in Microscopy1.1.25Required Practical - Microscopy1.1.26Microscopy - Calculations1.1.27Culturing Microorganisms1.1.28Contamination1.1.29Avoiding Contamination1.1.30Calculating Bacteria1.1.31Calculating Bacteria - Calculations1.1.32Required Practical - Bacteria1.1.33Exam-Style Questions - Cell Structure & Microscopy1.1.34Diagnostic Misconceptions - Converting1.1.35Diagnostic Misconceptions - Animal Cells1.1.36Diagnostic Misconceptions - Mitochondria1.1.37End of Topic Test - What's in Cells?
1.2

Cell Division

1.2.1Chromosomes1.2.2The Cell Cycle1.2.3Mitosis1.2.4Stem Cells1.2.5Use of Stem Cells1.2.6Disadvantages of Stem Cells1.2.7Exam-Style Questions - Mitosis & Cell Cycle1.2.8Diagnostic Misconceptions - Mitosis
1.3

Transport in Cells

1.3.1Diffusion1.3.2Factors Affecting Diffusion1.3.3Surface Area : Volume1.3.4Surface Area : Volume - Calculations1.3.5Exchange Surfaces1.3.6Examples of Exchange Surfaces1.3.7Osmosis1.3.8Osmosis 21.3.9Required Practical - Osmosis in Plant Tissue1.3.10Active Transport1.3.11Transport in Cells1.3.12Grade 9 - Cell Transport1.3.13Diagnostic Misconceptions - Water Moving1.3.14Diagnostic Misconceptions - Active Transport1.3.15End of Topic Test - Cell Division & Transport
2

Organisation

2.1

Principles of Organisation

2.1.1Cells & Tissues2.1.2Organs2.1.3Organ Systems2.1.4Organisms
2.2

Enzymes

2.2.1Enzymes2.2.2Enzymes HyperFlashcards2.2.3Rate of Reaction2.2.4Calculating Rate of Reaction2.2.5Rate of Reaction - Calculations2.2.6Digestion2.2.7Bile2.2.8Examples of Digestive Enzymes - Amylase2.2.9Examples of Digestive Enzymes - Protease2.2.10Examples of Digestive Enzymes - Lipase2.2.11Testing for Biological Molecules2.2.12Required Practical - Testing for Food Chemicals2.2.13Required Practical - Enzymes2.2.14Grade 9 - Enzymes2.2.15Exam-Style Questions - Enzymes2.2.16Diagnostic Misconceptions - High Temperatures2.2.17Diagnostic Misconceptions - Low Temperatures2.2.18Diagnostic Misconceptions - Stomach Acid2.2.19Diagnostic Misconceptions - Substrate Shape2.2.20End of Topic Test - Organisation & Enzymes
2.3

Circulatory System

2.3.1Types of Blood Vessels2.3.2Blood Vessels - Arteries2.3.3Blood Vessels - Capillaries2.3.4Blood Vessels - Veins2.3.5The Heart - Structure2.3.6The Heart - Function2.3.7Important Blood Vessels2.3.8Double Circulatory System2.3.9Gas Exchange2.3.10Gas Exchange - Calculations2.3.11Alveoli2.3.12Blood Components2.3.13Platelets2.3.14Red Blood Cells2.3.15White Blood Cells2.3.16End of Topic Test - Circulatory System
2.4

Non-Communicable Diseases

2.4.1Health Issues2.4.2Disease Interactions2.4.3Sampling2.4.4Sampling - Calculations2.4.5Risk Factors2.4.6Examples of Risk Factors2.4.7Risk Factor Graphs2.4.8Coronary Heart Disease2.4.9Heart Valve Disease2.4.10Heart Failure2.4.11Treating Heart Disease2.4.12Comparing Treatments of Heart Disease2.4.13Cancer2.4.14Cancer Risk Factors2.4.15End of Topic Test - Non-Communicable Diseases2.4.16Exam-Style Questions - Coronary Heart Disease
2.5

Plant Tissues, Organs & Systems

2.5.1Plant Organs2.5.2Leaves2.5.3Transpiration2.5.4Rate of Transpiration2.5.5Measuring Transpiration2.5.6Translocation2.5.7Transpiration Tissues - Xylem Cells2.5.8Transpiration Tissues - Root Hair Cells2.5.9Stomata2.5.10States of Stomata2.5.11Premium Knowledge - Transpiration2.5.12End of Topic Test - Plants2.5.13Exam-Style Questions - Plant Tissues2.5.14Diagnostic Misconceptions - Plant Food2.5.15Diagnostic Misconceptions - Plants & Water2.5.16Diagnostic Misconceptions - Plants Don't Breathe
3

Infection & Response

3.1

Communicable Disease

3.1.1Spreading Disease3.1.2Causing Diseases3.1.3Preventing Infection3.1.4Communicable Disease - Viruses3.1.5Examples of Viruses3.1.6Communicable Disease - Bacteria3.1.7Communicable Disease - Fungi3.1.8Communicable Disease - Protists3.1.9Human Defence Systems - Non-Specific Defences3.1.10Human Defence Systems - Immune Systems3.1.11Antibodies3.1.12Vaccinations3.1.13The Immune System3.1.14The Immune System 23.1.15Antibiotics3.1.16Antibiotic Resistance3.1.17Antibiotic Resistance 23.1.18Drug Discovery3.1.19Developing New Drugs3.1.20Drug Testing3.1.21Drug Testing in Laboratories3.1.22Double-Blind Trials3.1.23Drug Testing / Efficacy - Calculations3.1.24End of Topic Test - Communicable Diseases3.1.25Exam-Style Questions - Microorganisms & Disease3.1.26Diagnostic Misconceptions - Antibiotics
3.2

Monoclonal Antibodies

3.2.1Monoclonal Antibodies3.2.2Producing Monoclonal Antibodies3.2.3Uses of Monoclonal Antibodies3.2.4Grade 9 - Monoclonal Antibodies
3.3

Plant Diseases

3.3.1Ion Deficiencies in Plants3.3.2Plant Defences3.3.3Signs of Plant Disease3.3.4Identifying Disease3.3.5Other Plant Diseases3.3.6End of Topic Test - Antibodies & Plant Disease
4

Bioenergetics

4.1

Photosynthesis

4.1.1Photosynthesis4.1.2Photosynthesis Equation4.1.3Rate of Photosynthesis4.1.4Limiting Factors4.1.5Photosynthesis in Farming4.1.6Uses of Glucose4.1.7Photosynthesis - Calculations4.1.8Required Practical - Light Intensity4.1.9Grade 9 - Photosynthesis Experiment4.1.10Exam-Style Questions - Rate of Photosynthesis4.1.11Diagnostic Misconceptions - Photosynthesis4.1.12Diagnostic Misconceptions - Plants Respiration
4.2

Respiration

4.2.1Organisms and Energy4.2.2Respiration4.2.3Metabolism4.2.4Respiration - Calculations4.2.5Respiration During Exercise4.2.6Oxygen Debt4.2.7Respiration HyperLearning4.2.8End of Topic Test - Photosynthesis and Respiration4.2.9Exam-Style Questions - Anaerobic Respiration
5

Homeostasis & Response

5.1

Homeostasis

5.1.1Homeostasis5.1.2Regulating Internal Conditions5.1.3Homeostasis & Negative Feedback5.1.4The Body's Negative Feedback Loop5.1.5Exam-Style Questions - Exercise & Homeostasis
5.2

The Human Nervous System

5.2.1The Nervous System5.2.2The Nervous System HyperFlashcards5.2.3Synapses5.2.4Reflexes5.2.5Components of a Reflex Arc5.2.6Required Practical - Human Reaction Times5.2.7The Brain5.2.8Parts of the Brain5.2.9The Brain: Neuro Techniques5.2.10Retina Scanning5.2.11Eye Anatomy5.2.12Eye Function - Focus5.2.13Eye Function - Light5.2.14Eye Defects5.2.15Thermoregulation5.2.16Hot & Cold5.2.17Thermoregulation - Sweating & Shivering5.2.18Thermoregulation - Body Hair5.2.19Thermoregulation - Blood Vessels5.2.20Body Temperature HyperLearning5.2.21End of Topic Test - Human Nervous System5.2.22Exam-Style Questions - Nervous System5.2.23Diagnostic Misconceptions - Nervous System
5.3

Hormonal Coordination in Humans

5.3.1Endocrine Glands5.3.2The Endocrine System5.3.3Thyroxine5.3.4Adrenaline5.3.5Blood Glucose5.3.6Detecting Glucose5.3.7Diabetes5.3.8Type 1 Diabetes5.3.9Type 2 Diabetes5.3.10Water Balance5.3.11Kidneys5.3.12Urea5.3.13Urine Production5.3.14Urine5.3.15Dialysis5.3.16Dialysis - Pros & Cons5.3.17Transplants5.3.18Transplants - Pros & Cons5.3.19Puberty5.3.20Menstruation5.3.21Menstrual Hormones5.3.22Menstrual Cycle5.3.23Contraception - 'Natural Methods'5.3.24Contraception - Sterilisation5.3.25Contraception - Condoms5.3.26Contraception - The Pill5.3.27Contraception - Diaphragm & IUDs5.3.28Contraception - Other Options5.3.29Hormones for Infertility5.3.30In Vitro Fertilisation5.3.31Fertility Treatments - Pros & Cons5.3.32End of Topic Test - Homeostasis & Hormones5.3.33Grade 9 - Hormonal Coordination5.3.34Exam-Style Questions - Hormones & Contraception
5.4

Plant Hormones

5.4.1Plant Hormones5.4.2Types of Tropisms5.4.3Auxins & Tropisms5.4.4Effect of Light on Seedlings5.4.5Required Practical - Light or Gravity on Seedlings5.4.6Uses of Plant Hormones5.4.7End of Topic Test - Hormones
6

Inheritance, Variation & Evolution

6.1

Reproduction

6.1.1Cell Division6.1.2Meiosis6.1.3Sexual Reproduction6.1.4Asexual Reproduction6.1.5Sexual Reproduction Advantages6.1.6Asexual Reproduction Advantages6.1.7Genome6.1.8Genome - Diagram6.1.9Genome Sequencing6.1.10Nucleotide6.1.11DNA Structure6.1.12Protein Synthesis6.1.13Protein Synthesis 26.1.14Mutations6.1.15Alleles6.1.16Genotype vs Phenotype6.1.17Punnett Squares6.1.18Punnett Squares 26.1.19Inherited Disorders6.1.20Cystic Fibrosis Punnett Square6.1.21Family Trees6.1.22Polydactyly6.1.23Genetic Crosses - Calculations6.1.24Genome Screening6.1.25Disadvantages of Embryonic Screening6.1.26Sex Determination6.1.27End of Topic Test - Reproduction6.1.28Exam-Style Questions - DNA & Genetics6.1.29Diagnostic Misconceptions - Mutations6.1.30Diagnostic Misconceptions - Chromosomes6.1.31Diagnostic Misconceptions - Genes & Alleles
6.2

Variation & Evolution

6.2.1Variation6.2.2Evolution & Speciation6.2.3Natural Selection6.2.4Selective Breeding6.2.5Selective Breeding 26.2.6Uses of Selective Breeding6.2.7Dangers of Selective Breeding6.2.8Genetic Engineering6.2.9Genetic Engineering 26.2.10Uses of Genetic Modification6.2.11Advantages of Genetic Modification6.2.12Disadvantages of Genetic Modification6.2.13Cloning6.2.14Cloning Plants6.2.15Cloning Animals6.2.16Adult Cell Cloning6.2.17End of Topic Test - Variation & Evolution6.2.18Exam-Style Questions - Selective Breeding
6.3

Genetics & Evolution

6.3.1Natural Selection6.3.2Controversy Around Natural Selection6.3.3Darwin's Theory of Evolution6.3.4Inheritance Theory6.3.5Speciation6.3.6Alfred Russel Wallace6.3.7Evidence for Evolution6.3.8Fossils6.3.9Resistant Bacteria6.3.10Genetics6.3.11Extinctions6.3.12Grade 9 - Evolution6.3.13Diagnostic Misconceptions - Natural Selection
6.4

Classification

6.4.1Classification of Living Organisms6.4.2Traditional System6.4.3Classification of Living Organisms: Updated System6.4.4Evolutionary Trees6.4.5End of Topic Test - Genetics & Classification
7

Ecology

7.1

Adaptations & Interdependence

7.1.1Communities: Ecosystems7.1.2Communities: Resources7.1.3Species Interdependence7.1.4Stable Communities
7.2

Organisation of Ecosystems

7.2.1Population Dynamics7.2.2Predator-Prey Graphs7.2.3Impact of Environmental Change7.2.4Causes of Environmental Change7.2.5Assessing Ecosystems7.2.6Organism Abundance7.2.7Required Practical - Population Size7.2.8Assessing Ecosystems - Calculations7.2.9The Carbon Cycle7.2.10The Water Cycle7.2.11The Cycling of Materials7.2.12Decay7.2.13Anaerobic Decay7.2.14Biogas Generators7.2.15Required Practical - Decay7.2.16End of Topic Test - Organisation of Ecosystems7.2.17Grade 9 - Ecosystems7.2.18Exam-Style Questions - Decomposition
7.3

Biodiversity

7.3.1Humans & Biodiversity7.3.2Waste Management7.3.3Human Activities7.3.4Land Use7.3.5Deforestation7.3.6Carbon Dioxide7.3.7The Greenhouse Effect7.3.8Global Warming7.3.9Maintaining Biodiversity7.3.10End of Topic Test - Adaptations & Biodiversity
7.4

Trophic Levels

7.4.1Trophic Levels7.4.2Trophic Levels: Food Chains7.4.3Trophic Levels: Decomposers7.4.4Pyramids of Biomass7.4.5Transfer Efficiency7.4.6Reasons for Energy Wastage7.4.7Transfer Efficiency - Calculations7.4.8Premium Knowledge - Trophic Levels & Food Chains7.4.9Exam-Style Questions - Food Chains7.4.10Diagnostic Misconceptions - Arrows
7.5

Food Production

7.5.1Food Security7.5.2Food Production: Biotechnology7.5.3Declining Fish Stock7.5.4Sustainable Fishing7.5.5Farming7.5.6Food Production - Calculations7.5.7End of Topic Test - Food & Trophic Levels

Practice questions on Natural Selection

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Which of these conditions or outcomes is NOT connected to the process of natural selection?Multiple choice
  2. 2
    In natural selection:True / false
  3. 3
    Natural Selection Put in order
  4. 4
    Which of the following is an example of genetic variation within a species?Multiple choice
  5. 5
    Name three mechanisms of evolution:Fill in the list
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Evolution & Speciation

Selective Breeding