(external environment ques) What is the importnce of cells and organisms carrying out exchange with external environment

Paragraph 1 — Cell membrane exchange

Start small: cells

Talk about:

• diffusion

• osmosis

• active transport

Examples:

• glucose uptake into cells

• ions transported by sodium-potassium pump

• water movement by osmosis

Importance:

• supplies reactants for respiration

• maintains water potential

• maintains concentration gradients

Nice because it’s core biology.

Paragraph 2 — Gas exchange in mammals

Very strong paragraph.

Talk about Gas exchange at alveoli:

• oxygen diffuses into blood

• carbon dioxide diffuses out

Adaptations:

• large surface area

• thin exchange surface

• ventilation + blood flow

Importance:

• O₂ needed for aerobic respiration

• CO₂ removal prevents pH changes

Paragraph 3 — Digestion and absorption

Exchange with food in gut.

Talk about:

• digested molecules absorbed in ileum

• glucose via co-transport

• fatty acids via diffusion

Importance:

• provides monomers

• ATP production

• protein synthesis

Could mention Glucose specifically.

Paragraph 4 — Kidney / excretion

Very synoptic.

Talk about:

• ultrafiltration

• selective reabsorption

• excretion of urea

Importance:

• removes toxic nitrogenous waste

• regulates water potential

• ion balance

Link to homeostasis.

You can also mention Antidiuretic hormone here.

Paragraph 5 — Plants

Great for breadth (many students forget this).

Root hair cells

Exchange with soil:

• mineral ions by active transport

• water by osmosis

Leaves

Exchange with atmosphere via stomata:

• CO₂ in

• O₂ out

• water vapour out

Importance:

• photosynthesis

• transpiration stream

• mineral transport

This adds originality.

Paragraph 6— Ecosystems (if you want extra breadth)

Very essay-band-5.

Organisms exchange with environment through:

• nutrient cycling

• carbon cycle

• nitrogen cycle

Examples:

• plants absorb nitrates

• decomposers release nutrients

Shows exchange at ecosystem scale.