The importance of responses to your internal and external environment in organisms

Question 1

Fall in blood glucose levels

Answer 1

1) Alpha cells from Islets of Langerhans detect blood glucose decrease and secrete glucagon.
2) Travels in blood, reaching target cell, works by 2nd messenger system, causing glycogenolysis.
3) Gluconeogenesis synthesises glucose from amino acids and glycerol.
4) Blood glucose levels increase.

When there’s an increase, secretes insulin which undergoes glycogenesis. No insulin = low water potential = water leaves cells into blood = blood pressure increases = increased risk of heart attack.

Question 2

Low blood water potential

Answer 2

1) Detected by osmoreceptors in hypothalamus.
2) Hypothalamus makes more ADH.
3) ADH to blood via pituitary gland.
4) To get cells in DCT and CD to respond.
5) Walls of collecting duct/CT allows more water from filtrate -> blood.
6) Concentration of urine increases so drink more.

Water needed to hydrolyse glycogen to glucose which can be used in respiration. Without this, there will be less metabolic processes like muscle contraction. Also, cells dehydrate and shrivel.

Question 3

IAA in the shoot tip - phototropism

Answer 3

1) Cells in shoot tip produce IAA, diffuses down shoot.
2) Light causes movement of IAA from light side to shaded side.
3) Conc. greater in darker side.
4) Attaches to receptors on membrane of cells.
5) Releases hydrogen ions, lowering the pH.
6) Breaks bonds between microfibrils in the cellulose cell wall, making them more easily stretched so they elongate.
7) Shaded side grows faster = shoot bends towards the light.

Light needed for the light dependent reaction of photosynthesis so that NADP and ATP can be produced to be used in the light independent reaction

Question 4

Reproductive success through mutation and better adaptation to the environmental conditions

Answer 4

1) Organisms produce more offspring than can be supported.
2) Most populations remain relative constant in size.
3) Due to Intraspecific competition.
4) Random mutation of alleles within gene pool mean some will have combinations of alleles that make them more likely to survive.
5) These will have a better chance at breeding and passing on these alleles.
6) New offspring also have these advantageous alleles, pass them on by breeding.
7) Disadvantageous alleles decrease overtime.

Question 5

Geographical isolation giving rise to a new species

Answer 5

1) Individuals of a species can interbreed in the same area.
2) Habitat separates into two regions that becomes geographically isolated.
3) Abiotic and biotic conditions within two areas become different so selection pressures exist in two areas.
4) Within a population, there is genetic variation cuz gene mutation.
5) Mutations give rise to different phenotypes.
6) Organisms with phenotypes better able to survive are selected for, meaning they have greater reproductive success and pass on their alleles.
7) Over time, the differences between gene pools become so great that the two populations can no longer interbreed and produce living fertile offspring - speciation!