Biology B3+B4

1.Describe the role of a sensory neurone

Sensory neurones are nerve cells wishing the nervous system responsible for converting external stimuli from the organisms external environment into internal electrical impulses

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2.Give an example of an effector.

A muscle may contract

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3.Draw a diagram of a typical neurone and label all the parts.

.

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4.What is the purpose of a reflex action?

They're automatic so they're quicker than normal responses. They often have a protective role e.g. snatching back your hand when you touch a burning hot plate

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5.Describe the pathway of a reflex arc from stimulus to response.

1.Stimulus 2.Receptor 3.Sensory neurone 4.CNS 5.Motor neurone 6.Effector 7.Response

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6.What is the endocrine system?

Hormones are chemicals produced in various glands called endocrine glands. These glands make up your endocrine system

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7.Give one role of thyroxine in the body.

To regulate the metabolic rate-the speed at which the chemical reactions in the body occur

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8.Explain how negative feedback helps to control the level of thyroxine in the blood.

When level is too high TSH is secreted from the pituitary gland and is hesitant. This reduces the amount of thyroxine released from the thyroid gland so the level falls back to normal

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9.Describe the effect that adrenaline has on the body

When you brain detects a stressful situation, it sends nervous impulses to the adrenal glands which respond by secreting adrenaline. This gets the body ready for action

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10a.State where testosterone is produced and briefly explain its role in reproduction.

It's produced in the testes and stimulates sperm production. It's important for the development of the male reproductive system

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10b.State where oestrogen is produced and briefly explain its role in reproduction.

It's produced in the ovaries and is involved in the menstrual cycle. It promotes female sexual characteristics

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10c.State where progesterone is produced and briefly explain its role in reproduction.

Also produced by the ovaries and it helps to support pregnancy. It's involved in the menstrual cycle

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10d.State where FSH and LH are produced and briefly explain their role in reproduction.

They're released from the pituitary gland in the brain and they help to control the menstrual cycle

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11Explain how the combined pill prevents pregnancy when taken as a contraceptive.

The combined pill stimulates production of thick cervical mucus making it less likely that any sperm will get through and reach an egg. Also, oestrogen prevents ovulation by inhibiting FSH

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12.Describe how one non-hormonal method of contraception works and list its pros and cons.

IUDs is a t-shaped device containing copper.They're inserted into the uterus and prevent sperm from surviving.They also alter the lining of the womb so that fertilised eggs can't implant.99% effective+kept in for 10 years. But can't prevent STIs

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13.Why is it important to maintain steady conditions in the body?

Its vital for your metabolic reactions to continue at an appropriate rate

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14.Describe the roles of insulin and glucagon in controlling a person's blood sugar level.

Blood glucose level too high-insulin is added-insulin removes glucose from blood-blood level . Blood glucose level too low-glucagon is added-glucagon moves to liver and turns into glucose-glucose released into the blood-blood level

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15.Explain how type 1 and type 2 diabetes can be treated.

Type 1:Pancreas produces little insulin, so they inject insulin into the blood to stop level of glucose getting to high. Type2:Resistant to insulin causing blood sugar levels to rise to a dangerous level.Can be controlled by eating a healthy diet

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16.How does carbon in the atmosphere enter food chains?

Plants take in carbon+turn it to complex compounds that make up organisms.These are taken by animals when they eat plants.The elements are recycled+return to the environment as waste products,ready to be used by new plants and put back in food chain

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17.What is the role of microorganisms in the carbon cycle?

They break down dead organisms and waste products, then put the elements back into the soil

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18.What is the role of nitrogen-fixing bacteria in the nitrogen cycle?

They turn N into nitrogen compounds that plants can use

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19.Which microorganisms turn nitrates into N gas?

Denitrifying bacteria

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20.List the four main processes in the water cycle.

1.Sun turns water into water vapour+water evaporates from plants via transpiration.2.Water vapour travels up as warm air rises+it cools+condenses to form clouds.3.Precipitation-returns to land+sea.4.Flow of fresh water allows nutrients to be moved

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21.What is meant by the term 'population' in the organisation of ecosystems?

All the organisms of one species in a habitat

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22.Give four resources that plants compete for in ecosystems.

Light, space, water, minerals(nutrients)

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23.Suggest how light intensity might affect a community.

E.g.as trees grow and provide more shade, grasses may be replaced by fungi and mosses which are better able to cope with the low light intensity

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24.Give two biotic factors that affect communities in ecosystems.

Availability of food, number of predators

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25.Explain why the populations of predators and prey often change out of phase in cycles.

It takes a while for one population to respond to changes in the other population

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26.What is a parasitic relationship?

They take what they need to survive and don't give anything back

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Biology B3+B4

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