GCSE Combined Science Biology Paper 2 - Lecture Summary

Introduction

• Lecture by Emma covering the entire Biology Paper 2 for GCSE Combined Science.
• Differentiates between higher tier (marked) and foundation tier (non-marked sections).
• Emphasis on practicing questions alongside content.

Homeostasis and Response

Homeostasis

• Regulation of internal conditions to keep them constant.
• Important for enzyme effectiveness.
• Human homeostatic conditions:
  • Blood glucose concentration.
  • Water levels.
  • Body temperature (~37°C).
• Stimulus - Change in the environment triggering homeostasis.
• Receptor Cells - Detect environmental changes.
• Coordination Center - Processes info (e.g., brain, pancreas).
• Effectors - Carry out the response (muscles, glands).

Human Nervous System

• Five sense organs:
  • Eye (light), Nose (chemicals/smell), Tongue (chemicals/taste), Ear (sound/balance), Skin (pressure/temperature).
• Neurons - Nerve cells that transmit impulses:
  • Sensory, Relay, Motor neurons.
• Pathway: Receptor -> Sensory Neuron -> Relay Neuron -> Motor Neuron -> Effector.
• Synapses - Gaps between neurons where neurotransmitters diffuse.

Reflex Actions

• Rapid, automatic responses not involving the conscious brain.
• Important for protection and basic functions like breathing.

Endocrine System

• Composed of glands that secrete hormones into the bloodstream.
• Key Glands: Pituitary (master gland), Thyroid, Pancreas, Adrenal, Testes, Ovaries.
• Hormones and their effects:
  • Thyroxine (metabolic rate, growth), Adrenaline (fight or flight response).

Blood Glucose Control

• Insulin lowers blood glucose by facilitating uptake by cells or storage as glycogen.
• Glucagon raises blood glucose by converting glycogen back to glucose.
• Importance of maintaining glucose levels.

Diabetes

• Type 1: No insulin production, genetic, treated with insulin injections.
• Type 2: Insulin resistance, linked to obesity, managed with diet, exercise, and sometimes medication.

Reproductive Hormones

• Males: Testosterone from testes, stimulates sperm production.
• Females: Estrogen from ovaries, leads to menstrual cycle.
• Menstrual cycle hormones: FSH (egg maturation), LH (ovulation), Estrogen & Progesterone (uterus lining maintenance).

Contraception

• Hormonal Methods: Pill, Patch, Injection, Implant (prevent egg maturation/release).
• Non-Hormonal Methods: Barrier methods, IUDs, Surgical methods, Abstinence.

Infertility Treatments

• Fertility drugs stimulate ovulation.
• IVF involves fertilizing eggs outside the body and implanting embryos.

Inheritance, Variation, and Evolution

Reproduction Types

• Sexual Reproduction: Involves mixing genetic information, leads to variation.
• Asexual Reproduction: Involves one parent, offspring are clones.

DNA and Genome

• DNA is a polymer of nucleotides forming a double helix.
• Genes are DNA sections coding for proteins.
• Human genome sequencing aids in understanding diseases and evolutionary history.

Inheritance Keywords

• Alleles: Different forms of a gene.
• Phenotype: Physical characteristics.
• Genotype: Genetic makeup.

Punnett Squares

• Used to predict offspring genotypes and phenotypes.
• Probability of traits being inherited.

Genetic Disorders

• Polydactyly: Dominant allele causes extra digits.
• Cystic Fibrosis: Recessive allele causes thick mucus production.

Genetic Screening

• Screening embryos for genetic disorders, with ethical, economic, and social considerations.

Evolution

• Natural selection leads to evolution over time.
• Species may evolve into new species if sufficiently different.

Ecology

Ecosystems and Communities

• Ecosystems consist of biotic (living) and abiotic (non-living) components.
• Stable communities have balanced biotic and abiotic factors.

Biotic and Abiotic Factors

• Abiotic: Light, moisture, pH, temperature, etc.
• Biotic: Competition, predation, disease, etc.

Competition

• Animals compete for food, territory, and mates.
• Plants compete for light, space, water, and nutrients.

Adaptations

• Organisms have structural, behavioral, and functional adaptations to their environments.

Food Chains

• Show feeding relationships: Producer -> Primary Consumer -> Secondary Consumer -> Tertiary Consumer.
• Predator-prey cycles illustrate population dynamics.

Sampling and Quadrats

• Used to measure abundance and distribution of organisms.
• Transects and quadrats help assess environmental impact on species distribution.

Cycles

• Water Cycle: Water evaporates, condenses, and precipitates.
• Carbon Cycle: Includes respiration, combustion, photosynthesis.

Biodiversity and Human Impact

• Human activities like deforestation and pollution reduce biodiversity.
• Biodiversity is crucial for ecosystem stability.

Pollution and Waste

• Types: Land, air, water.
• Managing waste is crucial for reducing environmental impact.

Global Warming

• Caused by greenhouse gases (CO2, CH4) leading to climate change and habitat loss.

Conservation Efforts

• Breeding programs, habitat protection, sustainable practices aim to maintain biodiversity.