3.3.2

Plant Defences

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Plant Defences

Plants have lots of defences against infections and harm from other organisms. They include:

Physical defences

Physical defences

  • Bark is made of dead cells that acts as a barrier of protection for the stem against pathogens and pests (like aphids).
  • Waxy cuticle is a barrier on the surface of leaves and stems to stop pathogens invading leaf tissue.
  • Cell walls, which are made of cellulose, are a physical barrier to stop pathogens entering cells.
Chemical defences

Chemical defences

  • Antibacterial chemicals are produced by some plants, such as mint, garlic and witch hazel. They work like antibiotics to stop populations of bacteria from growing.
  • Poisons are produced by many plants, including foxglove and deadly nightshade, to deter (put off) herbivores.
Mechanical defences

Mechanical defences

  • Thorns or hairs stop animals eating the plants.
  • Leaves that close up rapidly when touched decrease the surface area available to herbivores. They may also dislodge smaller herbivores already on the plant.
  • Some plants use mimicry (copying) to trick animals.
    • An example is a pattern on leaves that resembles the presence of insect eggs. Insects avoid laying their eggs on them in order to avoid competition.
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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 Plant Defences

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

  1. 1
    Name the three categories of plant defence:Fill in the list
  2. 2
    A plant's mechanical defences are:True / false
  3. 3
    A plant's chemical defences include:True / false
  4. 4
    Name the two plant diseases which you have learned about through the biology course:Fill in the list
  5. 5
    Which of the following adaptations of a plant defence is described as mechanical?Multiple choice
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Ion Deficiencies in Plants

Signs of Plant Disease