11.3/3.5

Question 1

define osmoregulators

Answer 1

maintain a constant internal solute concentration, even when living in marine environments with very different osmolarities.

Question 2

3 examples of osmoregulators

Answer 2

• all terrestrial animals.
• freshwater animals.
• some marine organisms (eg. bony fish).

Question 3

define osmoconformers

Answer 3

animals whose internal solute concentration tens to be the same as the concentration of solutes in the environment.

Question 4

what is the form of waste product in insects vs mammals?

Answer 4

insects - uric acid
animals - urea

Question 5

define Malpighian tubules

Answer 5

tubes that branch off from insects’ intestinal tract.

Question 6

explain how insects secrete nitrogenous waste

Answer 6

• excreted as uric acid by Malpighian tubules
  1. ammonia accumulates in hemolymph
  2. ammonia absorbed by Malpighian tubules
  3. ammonia converted to uric acid
  4. conversion to uric acid requires energy
  5. high solute concentration in Malpighian tubules due to active transport of Na+/K+ into Malpighian tubules
  6. water absorbed by osmosis flushes uric acid/nitrogenous waste to hindgut
  7. water/ions reabsorbed from the feces and returned to hemolymph
  8. uric acid precipitates, becoming a solid so can pass out with little water
  9. uric acid excreted/egested with the feces
  10. water conservation/osmoregulation
  11. uric acid is non-toxic

Question 7

function of the kidney

Answer 7

osmoregualtion and excretion

Question 8

which substances are present in higher amounts in the renal artery than the renal vein?

Answer 8

• excretory waste products like urea
• excess water, produced by cell respiration or absorbed from food in the gut
• excess sal, absorbed from food in the gut

Question 9

outline the difference in water/salt concentrations in blood in the renal artery and vein.

Answer 9

blood in the renal artery might contain a variable water or salt content, whereas blood in the renal vein will have a more constant concentration because osmoregulation has occurred.

Question 10

3 ways in which metabolic activity of the kidney affects the composition of blood in the renal artery and vein

Answer 10

• blood leaving the kidney deoxygenated relative to the renal artery because kidney metabolism requires O2
• higher partial pressure of CO2 because this is a waste product of metabolism.
• some glucose is used by the metabolism of the kidney and therefore the concentration is slightly lower in the renal vein compared to artery.

Question 11

what substance is present in the same concentration in both the renal artery and vein?

Answer 11

plasma proteins, since they are not filtered by the kidney.

Question 12

site of ultrafiltration

Answer 12

Bowman’s capsule of nephron

Question 13

how is high hydrostatic pressure created in glomerulus?

Answer 13

diameter of afferent arteriole > diameter of efferent arteriole

Question 14

3 characteristics of ultrafiltration system

Answer 14

1. fenestrations: pores between the cells in the wall of the capillaries, which allow fluid to escape, but not blood cells.
2. podocytes: form the inner wall of the Bowman’s capsule. these cells have extensions that wrap around the capillaries of the glomerulus and many short side branches called foot processes. very narrow gaps between the foot processes help prevent small molecules from being filtered out of blood in the glomerulus.
3. basement membrane: covers and supports the wall of the capillaries. made of negatively-charged glycoproteins, which form a mesh. prevents plasma proteins from being filtered out, due to their size and negative charge.

Question 15

define the glomerular filtrate

Answer 15

fluid that passes through the glomerulus into the capsule space.

Question 16

role of the proximal convoluted tubule

Answer 16

selectively reabsorbs useful substances by active transport.

Question 17

describe how the kidney functions

Answer 17

check

Question 18

function of ADH

Answer 18

controls reabsorption of water in the collecting duct.

Question 19

if solute concentration of blood too high

Answer 19

hypothalamus of brain detects this and causes the pituitary gland to secrete ADH.

• this hormone causes the walls of the distal convoluted tubule and collecting duct to become more permeable to water, and most of the water in the filtrate is reabsorbed.
• this is helped by the solute concentration gradient of the medulla.
• as the filtrate passes down the collecting duct, it flows deep into the medulla, where the solute concentration of the interstitial fluid is high.
• water continues to be reabsorbed along the whole length of the collecting duct and the kidney produces a small volume of concentrated urine.
• consequently, the solute concentration of blood is reduced.

Question 20

define osmoregulation

Answer 20

control of solute concentrations and water balance.

Question 21

what is the form of nitrogenous water when animals break down amino acids and nucleic acids?

Answer 21

ammonia.

Question 22

why is ammonia problematic

Answer 22

• highly basic and can alter the pH balance.
• toxic as it is a highly reactive chemical.

Question 23

why can organisms that live in a marine or freshwater habitat release the waste directly as ammonia?

Answer 23

it can be easily diluted within that environment.

Question 24

what is the difference between converting ammonia to urea and converting ammonia to uric acid?

Answer 24

ammonia to uric acid requires even more energy.

Question 25

what is the advantage of uric acid?

Answer 25

it is not water-soluble and therefore does not require water to be released.

Question 26

which organisms release their nitrogenous waste as uric acid?

Answer 26

birds and insects.

Question 27

which organisms release their nitrogenous waste as urea?

Answer 27

- some terrestrial organisms. - mammals. - amphibians (release waste as urea after metamorphosis).

Question 28

how is uric acid linked to adaptations for reproduction?

Answer 28

- nitrogenous wastes are released by the developing organism within eggs. - uric acid is released as it is not soluble and crystallises rather than building up to toxic concentrations within the egg.

Question 29

what is dehydration?

Answer 29

a condition that arises when more water leaves the body than comes in. it can arise due to exercise, insufficient water intake or diarrhoea.

Question 30

consequences of dehydration

Answer 30

- tiredness and lethargy due to decreased efficiency of muscle function and increased tissue exposure to metabolic wastes. - blood pressure falls due to low blood volume which can lead to increases in heart rate. - body temperature regulation affected because of an inability to sweat.

Question 31

define over-hydration

Answer 31

an over-consumption of water.

Question 32

consequences of over hydration

Answer 32

- dilution of blood solutes. - body fluids become hypotonic and could result in the swelling of cells due to osmosis, leading to headache and nerve function disruption.

Question 33

describe hemodialysis

Answer 33

steady flow of blood passes over an artificial semi-permeable membrane in the dialysis machine. the small waste products in the blood pass through the membrane, but the larger blood cells and proteins cannot. the purified blood is then returned to the patient via the vein.

Question 34

treatments for kidney failure

Answer 34

hemodialysis or kidney transplant

Question 35

what are the advantages of kidney transplant instead of hemodialysis?

Answer 35

transplant results in greater independence of movement and freedom to travel as compared to dialysis. dialysis also carries the risk of infection and other complications.

Question 36

urinalysis

Answer 36

procedure that examines urine for any deviation from normal composition. this test indicates the pH, protein level and glucose level in the urine.

Question 37

high levels of glucose and protein in the urine indicate

Answer 37

- glucose: diabetes. - protein: damage to kidneys as these do not get through ultrafiltration in a healthy kidney.

Question 38

what does presence of white and red blood cells in the urine indicate?

Answer 38

- white blood cells can be sign of urinary tract infection. - red blood cells can be a sign that there is a kidney stone or a tumour in the urinary tract.

Question 39

define gel electrophoresis

Answer 39

separating charged molecules in an electric field, according to their size and charge.

Question 40

describe gel electrophoresis

Answer 40

1. samples are placed in wells cast in a gel. 2. the gel is immersed in a conducing fluid and an electric field is applied. 3. molecules in the sample that are charged will move through the gel. 4. molecules with negative and positive charges move in opposite directions (proteins may be + or - charged so can be separated).

Question 41

describe the gel used in gel electrophoresis

Answer 41

a mesh of filaments that resists the movement of molecules in a sample.

Question 42

why do DNA molecules from eukaryotes need to be broken down before gel electrophoresis?

Answer 42

too long to move through the gel.

Question 43

do smaller or larger fragments move through the gel faster?

Answer 43

small

Question 44

purpose of PCR

Answer 44

large numbers of copies of DNA.

Question 45

describe DNA profiling

Answer 45

A DNA sample is collected (e.g. from blood, semen, saliva, etc.) and then amplified using PCR Satellite DNA (with STR sequences) are cut with specific restriction endonucleases to generate fragments Fragment length will differ between individuals due to the variable length of their short tandem repeats The fragments are separated using gel electrophoresis and the resulting profiles are compared

Question 46

how is DNA profiling used in forensic investigations?

Answer 46

DNA profile of material from the crime scene is compared with the DNA profile of a sample of DNA taken from the suspect or the victim. if the pattern of bands matches exactly it is likely that the two samples of DNA are from same person.

Question 47

how is DNA profiling used in paternity investigations?

Answer 47

DNA profiles of the mother, the child and the man are needed, DNA profiles of each of the samples are prepared and the patterns of bands are compared. if any bands in the child's profile do not occur in the profile of the mother or man, another person must be the father.

Question 48

define genetic modification

Answer 48

the transfer of genes from one species to another.

Question 49

how is genetic modification possible?

Answer 49

since genetic code is universal, so when genes are transferred between species, the amino acid sequence translated from them is unchanged - the same polypeptide is produced.

Question 50

uses of genetic modification

Answer 50

- to introduce new characteristics to animal species. - to produce GM crops

Question 51

3 things involved in gene transfer to bacteria

Answer 51

Plasmids: - have genes that encourage their replication in the cytoplasm and transfer from one bacterium to another. - bacteria use plasmids to exchange genes, so naturally absorb them and incorporate them into their main circular DNA molecule. Restriction enzymes: - can be used to cut open plasmids and cut out desired genes from DNA molecules. - some restriction enzymes can cut the two strands of a DNA molecule at different points, leaving single-stranded sections called sticky ends. - sticky ends have complementary base sequences so can be used to link together pieces of DNA, by hydrogen bonding between the bases. DNA ligase: - when the desired gene has been inserted into a plasmid using sticky ends there are still nicks in each sugar-phosphate backbone of the DNA but DNA ligase can be used to seal the nicks.

Question 52

claims about environmental and agricultural benefits of GM crops

Answer 52

- pest-resistant crop varieties can be produced by transferring a gene for making a toxin to the plants. - GM crops reduce need for plowing and spraying crops, so less fuel is needed for farm machinery. - the shelf-life of fruit and veg can be improved, reducing wastage and area of crops that have to be grown. - varieties resistant to drought, cold and salinity can be produced by gene transfer, expending the range over which crops can be produced and increasing total yields. - a gene for herbicide resistance can be transferred to crop plants allowing all other plants to be killed in the growing crop by spraying with herbicide. with less weed competition crop yields are higher. - crop varieties can be produced that are resistant to diseases caused by viruses.

Question 53

claims about the health benefits of GM crops

Answer 53

- nutritional value of crops can be improved, eg. increasing the vitamin content. - varieties of crops could be produced lacking allergens or toxins that are naturally present in them. - GM crops could be engineered that produce edible vaccines so by eating the crop a person would be vaccinated against a disease.

Question 54

health risks of GM crops

Answer 54

- proteins produced by transcription and translation of transferred genes could be toxic or cause allergic reactions in humans or livestock that eat GM crops. - antibiotic resistance genes used as markers during gene transfer could spread to pathogenic bacteria. - transferred genes could mutate and cause unexpected problems that were not risk-assessed during development of GM crops.

Question 55

environmental and agricultural risks of GM crops

Answer 55

- non-target organisms could be affected by toxins that are intended to control pests in GM crop plants. - genes transferred to crop plants to make them herbicide resistant could spread to wild plants, turning them into uncontrollable super-weeds. - biodiversity could be reduced if a lower proportion of sunlight energy passes to weed plants as there are plant-eating insects and organisms that feed on them. - some seed from a crop is always spilt and germinates to become unwanted volunteer plants that must be controlled. - widespread use of GM crops containing a toxin that kills insect pests will lead to the spread of resistance to the toxin.

Question 56

define a clone

Answer 56

groups of genetically identical organisms, derived from a single original parent cell.

Question 57

cloning of garlic bub

Answer 57

a single garlic bulb, when planted, uses its food stores to grow leaves. these leaves produce enough food by photosynthesis to grow a group of bulbs. all the bulbs in the group are genetically identical so they are a clone.

Question 58

cloning strawberry plants

Answer 58

a strawberry plant grows long horizontal stems with plantlets at the end. these plantlets grow roots into the soil and photosynthesise using their leaves, so they can become independent of the parent plant.

Question 59

define stem cuttings

Answer 59

short lengths of stem that are used to clone plants artificially

Question 60

what is a pluripotent cell?

Answer 60

cells that are capable of developing into many, but not all, types of the body's cells.

Question 60

define splitting/fragmentation of an embryo

Answer 60

when the embryo divides into two or more parts and each part can develop into a separate individual with all body parts.

Question 61

how can IVF be used to produce clones of an embryo and why is this a limited method?

Answer 61

individual cells can be separated from the embryo while they are still pluripotent and transplanted into surrogate mothers. only a limited number of clones can be obtained this way, because after a certain number of divisions the embryo cells are no longer pluripotent. splitting of embryos is usually most successful at the eight-cell stage

Question 62

why is artificial cloning by separation of an embryo not popular

Answer 62

because at the embryo stage it is not possible to assess whether a new individual produced by sexual reproduction has desirable characteristics.

Question 63

describe the method of production for Dolly the Sheep

Answer 63

somatic-cell nuclear transfer: 1. adult cells were taken from the udder of a Finn Dorset ewe and were grown in the lamb using a medium containing a low concentration of nutrients. this made genes in the cells inactive so that the pattern of differentiation was lost. 2. unfertilised eggs were taken from the ovaries of a Scottish Blackface ewe. the nuclei were removed from these eggs. one of the cultured cells from the FD was placed next to each egg cell, inside the zone pellucid around the egg. 3. a small electric pulse was used to cause the two cells to fuse together. about 10% of the fused cells developed like a zygote into an embryo. 4. the embryos were then injected when about seven days old into the uteri of other ewes that could act as surrogate mothers. only 1 of the 29 embryos implanted successfully and developed through a normal gestation - this was Dolly.