Homeostatis, Resonse, Inheritance, Variation evolution Flashcards Preview

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Flashcards in Homeostatis, Resonse, Inheritance, Variation evolution Deck (28):

Explain how negative feedback helps to maintain a stable internal environment.

When a level of something gets too high or low your body uses negative feedback to bring it back to normal.


What makes up the central nervous system and what does it do?

Central Nervous system
Sensory Neurones
Motor Neurones
The central nervous system is a coordination centre - it receives information from the receptors and then coordinates a response. The response is carried out by the effectors.


What is a Synapse?

The connection between two neurones.


What is the purpose of a reflex action?

Reflexes help prevent injury:
Reflexes are rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain - they can reduce the chances of being injured.


Give two differences between nervous and hormonal responses.

nervous reactions don't involve the conscious part of the brain.
e.g if someone shines a bright light in your eyes, your pupils automatically get smaller so that less light gets into the eye - this stops its getting damaged.
If you get a shock, your body releases the hormone adrenaline automatically - it doesn't wait for you to 'decide' that you're surprised.


What effect does the hormone glucagon have on blood glucose level?

Level of glucose in the blood must be kept steady. Any changes are monitored and controlled but the pancreas, using hormones insulin and glycogen.


Describe two effects of FSH on the body.

FSH (follicle- stimulating Hormone)
1. produced in the pituitary gland.
2. Causes egg to mature in one of the ovaries in a structure called a follicle.
3. Stimulates the ovaries to produce oestrogen.


Which of the following is a hormonal contraceptive: condom, plastic IUD, or diaphragm?

Plastic IUD


Briefly describe how IVF is carried out.

1. collect eggs from womens ovaries and fertilise them in lab using sperm.
2. Intra Cytoplasmic Sperm Injection where sperm is directly injected into an egg.
3. Ferilised eggs are grown into embryos in incubator.
4. When embryos are tiny balls of cells one or tw are transferred to womens uterus.
5. FSH and LH are given before egg collection to stimulate severe eggs to mature.


How does adrenaline prepare the body for 'fight or flight'

It triggers mechanisms that increase supply of oxygen and glucose to cells in the brain and muscles. For example, adrenaline increases heart rate.


What is meant by double helix?

Two strands of DNA coiled together in the shape of double helix.


What do genes code for?

Genes each code for particular sequence of amino acids which are put together to make specific protein.


What is the name for the entire set of genetic material in an organism?



Name the male and female gametes of animals.

egg and sperm.


State the type of cell division used to make gametes in humans.



What is the probability that offspring have the XX combination of sex chromosomes?



What are alleles?

Different versions of genes


What does it mean if someone is heterozygous for a gene?

If its two alleles for a particular gene are different, then its heterozygous.


What is the chance of a child being born with polydactyly if one parent has a single dominant allele for the gene that controls it?

50% chance.


Give two arguments for and two arguments against screening embryos for genetic disorders.

it will help stop people suffering
Treating disorders costs the governments a lot of money
There are laws to stop it going too far. At the moment parents cannot even selects the sex of their baby.
It implies that people with genetic problems are 'undesirable' - could create prejudice.
There may come a time when everyone wants to screen their embryos so they can pick the most 'desirable' one
Screening is expensive.


what is variation?

Organisms of the same species looking different.


Explain how beneficial characteristics can become more common in a population over time.

'survival of the fittest'
Successful organisms are more likely to reproduce and pass on the genes that made them successful to their offspring.


How might farmers use selective breeding?

To improve yields for e.g: breeding cows and bulls together for producing meat (large size), after doing this for many generations the farmer would result in cows with very high meats yields.


What is genetic engineering?

To transfer gene responsible for a desirable characteristic from one organisms genome to another organism, so that it also has the desired characteristic.


Give two ways that fossils can be formed.

Gradual replacement of minerals:
things like teeth, shells and bones don't decay easily; they're eventually replaced by minerals as they decay forming rock-like substance; the surrounding sediments also turn to rock but fossil stays distinct inside the rock.
Cast abd impressions:
When an organism is buried in a soft material like clay. The clay later hardens around it and organism decays leaving a cast of itself.


What leads to the formation of antibiotic-resistant strains of bacteria?

Bacteria can develop random mutations which can become antibiotic resistant strains.


Name the groups that organisms are classified into in the Linnaean system.

Phylum, class, order, family, genus, species.


Who proposed the 'three-domain system' of classification in 1990?

Carl Woese