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Unit 3: Energy, Homeostasis and the Environment

7 dot points across 7 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does the body keep its internal conditions stable, and how does the kidney work?

The principles of homeostasis and negative feedback, the structure and function of the kidney, ultrafiltration, selective reabsorption and osmoregulation.
A focused answer to WJEC A-Level Biology Unit 3, covering the principles of homeostasis and negative feedback, the structure of the kidney and nephron, ultrafiltration, selective reabsorption, and osmoregulation by ADH.
11 min answer →

How do human activities affect biodiversity and the environment?

The effects of human activity on biodiversity, deforestation and agriculture, pollution and climate change, and conservation.
A focused answer to WJEC A-Level Biology Unit 3, covering the effects of human activity on biodiversity, deforestation and intensive agriculture, pollution including eutrophication, climate change, and conservation strategies.
11 min answer →

How do plants capture light energy and store it as chemical energy?

The role of ATP, the light-dependent and light-independent reactions of photosynthesis, and the factors that limit the rate.
A focused answer to WJEC A-Level Biology Unit 3, covering the role of ATP, the light-dependent reactions and photophosphorylation, the light-independent Calvin cycle, and the factors limiting the rate of photosynthesis.
11 min answer →

How do we grow and count microorganisms safely?

The structure of bacteria, aseptic technique, culturing microorganisms, the growth curve, and methods of measuring growth.
A focused answer to WJEC A-Level Biology Unit 3, covering bacterial structure, aseptic technique, culturing microorganisms in batch and continuous culture, the bacterial growth curve, and methods of measuring microbial growth.
11 min answer →

What controls the size of populations and the flow of energy through ecosystems?

Ecosystems, energy flow and nutrient cycles, population growth and the factors that limit it, and succession.
A focused answer to WJEC A-Level Biology Unit 3, covering ecosystems and trophic levels, energy flow and the carbon and nitrogen cycles, population growth and limiting factors, and succession.
11 min answer →

How do cells release energy from glucose to make ATP?

Glycolysis, the link reaction, the Krebs cycle, oxidative phosphorylation, and anaerobic respiration.
A focused answer to WJEC A-Level Biology Unit 3, covering glycolysis, the link reaction, the Krebs cycle, oxidative phosphorylation and the electron transport chain, and anaerobic respiration in animals and yeast.
11 min answer →

How do nerve cells carry and pass on electrical signals?

The structure of neurones, the resting and action potentials, conduction of nerve impulses, and synaptic transmission.
A focused answer to WJEC A-Level Biology Unit 3, covering neurone structure, the resting potential, the action potential, saltatory conduction along myelinated neurones, and transmission across a cholinergic synapse.
11 min answer →