Responses to a Changing Environment

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Homeostasis

Sensitivity

Skin Sensitivity: PCA

Responding to stimuli

Hormones

Diabetes

Tropic Responses: PCA

Plant Hormones

Uses of plant hormones


What you should be able to do:

EDEXCEL GCSE Science BIOLOGY UNIT B1 Influences on life

Topic 2 Responses to a changing environment

• 2.1 Be able to define homeostasis as the maintenance of a stable internal environment in an organism.
• 2.2 You must have an understanding of the homeostatic mechanisms of:
  • a) thermoregulation and the effect of temperature on enzymes
  • b) osmoregulation
  • c) blood glucose regulation
• 2.3 Be able to explain how thermoregulation takes place, with reference to the function of the skin, including:
  • a) the role of the dermis – sweat glands, blood vessels and nerve endings, hair, erector muscles and sebaceous glands
  • b) the role of the hypothalamus – regulating body temperature
• 2.4 HT only: Be able to explain how thermoregulation takes place, with reference to:
  • a) vasoconstriction
  • b) vasodilation
  • c) negative feedback
• 2.5 Know that hormones are produced in endocrine glands and are transported by the blood to their target organs
• 2.6 Be able to explain how blood glucose levels are regulated by insulin and excess blood glucose is converted to glycogen in the liver
• 2.7 HT only: Be able to explain how blood glucose levels are regulated by glucagon causing the conversion of glycogen to glucose
• 2.8 Know that Type 1 diabetes is caused by a lack of insulin, the hormone which controls the level of glucose in the blood
• 2.9 Be able to explain how Type 1 diabetes can be controlled, including the roles of diet and injection of insulin usually into the subcutaneous fat
• 2.10 Be able to explain how, in Type 1 diabetes, the level of physical activity and diet affect the amount of insulin required
• 2.11 Know that Type 2 diabetes is caused by a person becoming resistant to insulin
• 2.12 Be able to explain how Type 2 diabetes can be controlled by diet and physical activity
• 2.13 Be able to evaluate the correlation between obesity (including calculations of BMI) and Type 2 diabetes
• 2.14 Be able to explain how plant growth substances (hormones) bring about: a positive phototropism in shoots b positive gravitropism (geotropism) in roots
• 2.15 Be able to explain how auxins bring about shoot curvature using cell elongation
• 2.16 You are expected to have investigated, and therefore have some knowledge of tropic responses.
• 2.17 Be able to analyse, interpret and evaluate data from plant hormone experiments, including the action of auxins and gibberellins
• 2.18 HT only: You should have an understanding of the uses of plant hormones, including:
  • a) selective weedkillers
  • b) rooting powder
  • c) seedless fruit
  • d) fruit ripening
• 2.19 Know that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves.
• 2.20 Be able to explain the structure and function of dendrons and axons in the nervous system.
• 2.21 Be able to describe how stimulation of receptors in the sense organs sends electrical impulses along neurones.
• 2.22 You are expected to have investigated human responses to external stimuli and therefore have some knowledge of these phenomena.
• 2.23 You need to be able to describe the structure and function of sensory, relay and motor neurones and synapses including:
  • a) the role of the myelin sheath
  • b) the role of neurotransmitters
  • c) the reflex arc