biology paper 2

homeostasis

all the processes happening in a cell or organism to maintain conditions optimal. needed to respond to changes in the internal and external environment

optimum conditions have to be kept for the enzyme functioning and if they are not optimal our enzymes can denature

reflex arc

reflex pathway: stimulus → receptor→ sensory neurone → relay neurone → motor neurone → effector → response

endocrine system

hormones like adrenaline insulin and glucagon and how the pancreas regulates blood glucose levels

hormone

a chemical substance produced by a gland and carried in the bloodstream which alters activity of specific target organ. Once a hormone is used it is destroyed by the liver.

adrenal gland

releases hormorne adrenaline which increases the heart rate

glucose

is a simple sugar and it is needed by cells for respiration. its important that the concentration of glucose in the blood is maintained at a constant level.

insulin

is a hormone produced by the pancreas regulating glucose concentrations in the blood. it causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage and will be used at a later date

type one diabetes

pancreas fails to produce enough insulin characterised by uncontrolled high blood glucose levels. can be controlled by injecting insulin. People with type one diabetes have to monitor their blood sugar levels throughout the day and can help control blood glucose levels by exercising or having a low sugar diet.

type two diabetes

In type two diabetes persons cells do not respond to insulin and it is more common in obese and older people. controlled by a carbohydrate controlled diet and regular exercise

synapse

gap between two nerve cells where first neuron releases chemicals called neurotransmitters which move across the gap to trigger a new electrical signal in the receiving cell.

Oestrogen

primary female reproductive hormone produced in the ovaries. it thickens the Uterus walls by stimulating growth and repair preparing uterus for fertilized egg.

triggers ovulation

FSH

follicle stimulating hormone released by the pituitary gland which causes an egg to mature and stimulates estrogen

DNA

polymer made up of two strands forming double helix. creates a chromosome

phenotype

physical characteristic of an organism it is the visible result of genes interacting with environment

genotype

collection of alleles an organism has for example if someone has genotype Bb (dominant brown allele and one recessive blue allele) their phenotype is brown eyes.

required practical sampling ecosystems random

1. set grid over sampling area

2. use random number generator to obtain coordinates

3. place quadrant at those coordinates and count target organisms

4. repeat at least 10 times to ensure data is representative and reliable

5. total population = (total area over sampled area) times by number of organisms counted