BIOLOGY UNIT 1 AOS 2

Transpiration

The loss of water vapour from plant surfaces, mainly through stomata in leaves. It creates negative pressure that pulls water upward through the xylem roots to leaves.

Xylem

The vascular tissue that transports water and dissolved minerals from roots to the rest of the plant (root to shoot). It provides the pathway for water needed for transpiration and photosynthesis, and it helps maintain water balance by replacing the water lost from leaves during transpiration.

Stomata

Stomata are tiny openings on the surface of leaves, and guard cells surround them to control whether they open or close. When stomata are open, carbon dioxide diffuses into the leaf for photosynthesis, while oxygen and water vapour diffuse out; this supports gas exchange but also causes water loss through transpiration. Guard cells help maintain water balance by opening the stomata when the plant needs gas exchange and closing them when water loss needs to be reduced.

Environmental factors affecting transpiration and how they affect the rate of transpiration

Solar radiation, wind, humidity (watch vid to elaborate more info on here)

Why are transpiration rates higher when photosynthesis is high?

Transpiration rates are higher when photosynthesis is high because the stomata need to open wider to let more carbon dioxide in for photosynthesis. When the stomata are open, more water vapour can escape at the same time, so transpiration increases too.

What is the role of homeostasis in the body?

• How does it maintain internal environments within the optimum functioning range?

Homeostasis means maintaining stable internal conditions (within its tolerance range or certain limits) despite changes in either the internal or external environments. The body achieves homeostasis by utilising negative feedback loops to bring the body back to a normal state.

How can external temperature affect the body’s homeostatic control mechanisms?

External temperatures affect the body’s ‘core temperature’ (36.1–39 °C) by forcing homeostatic mechanisms to adjust. To maintain the internal environment within its optimum range, the nervous system detects this stimulus, processes the temperature input and triggers a corrective physiological response.

What responses occur to maintain homeostasis when external temperatures change?

Too hot:

• sweating (sweat glands are activated)

• vasodilation (blood increases towards the surface so the air can cool it down & the heat can radiate away from the body)

• behavioural changes (reducing physical acitvity, taking off a layer, taking shade)

Too cold:

• vasostriction: The blood travels towards the body to conserve heat

• shivering (muslces in the body contract to build heat)

• metabolic adjustment (The endocrine system may release hormones that increase the body's metabolic rate, producing more internal heat)

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What role does negative feedback play in homeostasis?

• How does it help return the body to the set point when a change has been detected?

What is positive feedback, and how does it differ from negative feedback

• How does positive feedback amplify the stimulus and take the body further from normal conditions?

How can the stimulus-response model and negative feedback be used to illustrate the homeostatic regulation of a variable in the human body?

(TO BE EDITED!!!)

The stimulus-response model in homeostasis follows a negative feedback loop: a stimulus (change in a variable) is detected by receptors, processed by a control center (like the brain), and corrected by effectors to return conditions to a set point. This prevents harmful deviations and maintains optimal functioning

What is the role of insulin, glucagon, and the liver in glucose regulation, and how do beta and alpha cells contribute to this process?

(TO BE EDITED!!!)

Glucose from digested carbohydrates is regulated by the pancreas: beta cells release insulin to lower blood glucose by promoting its uptake into cells and conversion to glycogen in the liver; alpha cells release glucagon to raise it by breaking glycogen back into glucose. The liver acts as a storage and conversion hub, ensuring steady energy supply

How does the body achieve osmoregulation, specifically involving the hypothalamus, the pituitary gland, ADH, and the kidney nephron tubules, and why is this process essential?

(TO BE EDITED!!!)

Osmoregulation maintains blood plasma water levels: hypothalamic receptors detect high solute concentration, signaling the pituitary to release ADH, which makes kidney nephron tubules reabsorb more water to dilute plasma. This prevents dehydration or overhydration, crucial for cell function, enzyme activity, and blood pressure stability.

How can the stimulus-response model be applied to explain the body's physiological responses to cold and heat during thermoregulation?

(TO BE EDITED!!!)

For cold: stimulus (low temperature) triggers vasoconstriction, shivering, and goosebumps to conserve/generate heat. For heat: high temperature prompts vasodilation and sweating for cooling. The hypothalamus coordinates these via negative feedback to keep core temperature near 37°C

What are the key differences between Type 1 and Type 2 diabetes?

How is glucose regulation impacted in a person suffering from Type 1 diabetes?

What roles do insulin and glucagon play in glucose regulation and managing diabetes?

What are the symptoms of diabetes, and why do they occur?