D3-D4 Revision Guide: Continuity and Change: Organisms & Ecosystems

Reproduction

1. Sexual vs Asexual Reproduction

   • Sexual: Involves two parents; offspring are genetically diverse.

   • Asexual: One parent; offspring are genetically identical to the parent.

2. Role of Meiosis in Variation

   • Meiosis shuffles genes through independent assortment and crossing over, producing genetically unique gametes.

3. Male vs Female Sexes

   • Males: Produce sperm in testes; generally smaller gametes.

   • Females: Produce eggs in ovaries; generally larger gametes and provide more parental investment.

4. Diagrams of Reproductive Systems

   • Male: Includes testes, vas deferens, urethra, penis.

   • Female: Includes ovaries, fallopian tubes, uterus, vagina.

5. Annotations

   • Each part should be labelled with its function (e.g., testes produce sperm, uterus houses embryo).

6. Hormonal Regulation of Menstrual Cycle

   • FSH and LH stimulate ovulation; estrogen and progesterone regulate lining of uterus.

7. Fertilisation Sequence

   • Sperm meets egg in fallopian tube → zygote forms → implantation in uterus.

8. Hormones in IVF

   • Hormones stimulate egg production and control ovulation to retrieve eggs for fertilisation.

9. Plant Sexual Reproduction

   • Involves pollen from anther fertilising ovule in ovary, leading to seed development.

10. Insect-Pollinated Flower Features

• Bright petals, scent, nectar, sticky pollen to attract and stick to insects.

11. Insect-Pollinated Flower Diagram

• Label petals, anthers, stigma, style, ovary, sepals.

12. Cross-Pollination Strategies

• Includes timing of flowering, flower structure, and separation of sexes to avoid self-pollination.

13. Self-Incompatibility in Plants

• Genetic mechanisms prevent self-fertilisation, increasing genetic diversity.

14. Seed Dispersal & Germination

• Dispersal methods: wind, water, animals. Germination needs water, oxygen, and right temperature.

Inheritance

1. Haploid & Diploid Fusion

   • Haploid gametes (1 set of genes) fuse to form a diploid zygote (2 sets).

2. Genetic Crossing in Plants

   • Cross-pollinate manually between plants with desired traits to study inheritance.

3. Genotype vs Phenotype

   • Genotype: Genetic makeup (e.g., Bb).

   • Phenotype: Observable traits (e.g., brown eyes).

4. Dominant vs Recessive Alleles

   • Dominant masks recessive; recessive only shown when both alleles are recessive.

5. Phenotypic Plasticity

   • Traits can change due to environment (e.g., tanning, muscle growth).

6. Phenylketonuria (PKU)

   • Genetic disorder: cannot break down phenylalanine; causes brain damage if untreated.

7. Variation in Gene Pool

   • Caused by mutation, meiosis, and sexual reproduction.

8. Blood Type Inheritance

   • A, B, AB, and O types result from multiple alleles (IA, IB, i) and codominance.

9. Incomplete Dominance vs Codominance

   • Incomplete: Blended traits (red + white = pink).

   • Codominance: Both traits visible (AB blood type).

10. Sex Determination in Humans

    • Sperm contributes X or Y; XX = female, XY = male.

11. Haemophilia (Sex-linked Disorder)

    • X-linked recessive; mainly affects males due to only one X chromosome.

12. Pedigree Charts

    • Used to trace inheritance patterns of traits through generations.

13. Continuous vs Discrete Variation

    • Continuous: Many possible values (e.g., height).

    • Discrete: Fixed categories (e.g., blood type).

14. Box-and-Whisker Plots

    • Visual representation of data spread (median, quartiles, range).

Homeostasis

1. Homeostasis Definition

   • Maintaining internal balance (e.g., body temperature, pH, glucose levels).

2. Negative Feedback

   • Process where the body reverses a change to maintain stability (e.g., sweating cools you down).

3. Pancreatic Hormones and Glucose

   • Insulin lowers blood glucose; glucagon raises it.

4. Negative Feedback in Glucose Regulation

   • If glucose rises, insulin reduces it; if it falls, glucagon increases it.

5. Diabetes Types

   • Type 1: No insulin production.

   • Type 2: Insulin resistance.

6. Thermoreceptors & Hypothalamus

   • Thermoreceptors detect temperature changes; hypothalamus controls response.

7. Temperature Regulation Mechanisms

   • Sweating, shivering, vasodilation/constriction.

D.4 - Natural Selection

1. Natural Selection Basics

   • Fitter organisms survive and reproduce, passing on advantageous traits.

2. Mutation & Sexual Reproduction in Variation

   • Mutation adds new alleles; sexual reproduction mixes genes.

3. Biotic & Abiotic Selection Pressures

   • Biotic: Predators, disease.

   • Abiotic: Climate, food availability.

4. Adaptation, Survival, Reproduction

   • Traits that aid survival/reproduction become more common.

5. Heritable Changes

   • Only genetic changes passed on can drive evolution.

6. Sexual Selection

   • Traits that improve mating success (e.g., peacock feathers).

7. Simulations of Selection Pressure

   • Model how traits change under environmental stress.

Stability & Change

1. Ecosystem Stability

   • Ability to remain balanced over time (e.g., coral reefs, rainforests).

2. Factors & Tipping Points

   • Disturbances (like deforestation) can push systems past recovery.

3. Models to Investigate Stability

   • Simulations help predict outcomes of changes (e.g., species removal).

4. Keystone Species

   • Crucial for ecosystem function (e.g., wolves in Yellowstone).

5. Sustainability of Resource Harvesting

   • Sustainable practices avoid depleting resources long-term.

6. Sustainable Agriculture

   • Includes crop rotation, organic farming, minimal pesticide use.

7. Eutrophication

   • Excess nutrients → algal bloom → oxygen depletion → dead zones.

8. Biomagnification

   • Pollutants increase in concentration up the food chain.

9. Plastic Pollution

   • Micro- and macroplastics harm marine life and ecosystems.

10. Ecosystem Restoration

    • Rewilding and reintroducing species restore natural processes.

Climate Change

1. Anthropogenic Climate Change

   • Human-caused; due to fossil fuel burning, deforestation, etc.

2. Positive Feedback in Warming

   • Warming causes changes that amplify warming (e.g., ice melting reduces reflectivity).

3. Boreal Forest Tipping Point

   • Warming shifts forests from carbon sinks to sources.

4. Melting Ice Effects

   • Loss of sea/land ice alters habitats and sea levels.

5. Ocean Currents & Nutrients

   • Warming disrupts currents and nutrient cycles, affecting marine life.

6. Species Range Shifts

   • Warming forces species to move (e.g., coral bleaching, changing fish ranges).

7. Carbon Sequestration Solutions

   • Planting trees, restoring wetlands lock away carbon.