Biology paper two model exam question answers

Question 1

compare meosis and mitosis (8)

Answer 1

MITOSIS
two daughter cells
one cell division
full number of chromosomes
genetically identical cells
MEIOSIS
one daughter cell
two cell divisions
half number of chromosomes
genetically different cells

Question 2

describe how to use a rule drop to work out reaction time (4)

Answer 2

hold ruler above hand of other student
drop ruler so that other person catches it
record where ruler is caught
use conversion table to turn distance in mm into seconds

Question 3

how could we more accurately measure reaction time

Answer 3

use a computer programme

Question 4

what is a reflex?

Answer 4

a fast, automatic response that does not go to the conscious part of the brain

Question 5

how does the nervous system co-ordinate the reflex action (5)

Answer 5

receptor detects stimulus
impulse passes along sensory neuron
crosses synapse via chemicals to the relay neuron
in the spinal cord or central nervous system
passes along motor neuron to effector/muscle

Question 6

how does information pass across a synapse?

Answer 6

chemical diffuses across synapse, binds to receptors on next neuron

Question 7

what is a hormone?

Answer 7

a chemical messenger that is released into the blood stream by a gland and travels through the blood stream

Question 8

describe how hormones control the menstrual cycle (4)

Answer 8

FSH produced in the pituitary gland- matures an egg
Oestrogen produced in the ovaries- thickens uterus lining and inhibits release of FSH
LH produced in pituitary gland- ovulation
progesterone produced in ovaries- inhibits LH and FSH and keeps uterus lining thick

Question 9

explain the effect of insulin on blood glucose concentration (5)

Answer 9

insulin released by pancreas
effects liver cells
causes more glucose to be taken into cells
causes glucose to change into glycogen
blood glucose concentration increases

Question 10

explain the effect of glucagon on blood glucose concentration (4)

Answer 10

glucagon released by pancreas
effects liver cells
causes glycogen to turn into glucose
blood glucose concentration increases

Question 11

describe the process of IVF (5)

Answer 11

FSH and LH given to mature egg
eggs collected from ovaries
fertilized with sperm
egg divides to form embryos
embryo inserted into uterus

Question 12

explain how blood vessels in the skin can decrease body temperature (4)

Answer 12

blood vessels supplying the skin dilate
more blood flow near surface of skin
more heat/energy is lost from blood
cools blood which cools body

Question 13

describe how plants grow towards the light (4)

Answer 13

make auxin in tip of shoots auxin
auxin moves to shaded side of plant
stimulates more cell growth on shaded side
so bends towards light

Question 14

describe how the water content of the blood is controlled when it is too low (3)

Answer 14

if water content of blood too low, ADH released from pituitary gland
increases permeability of tubules in kidney
more water reabsorbed into blood

Question 15

explain how a persons eye adjusts to form a clear image of a near object (5)

Answer 15

cilliary muscles contract
suspensory ligaments loosen
lens thickens/becomes more curved
lens refracts light more
light rays more focused on retina

Question 16

explain how a persons eye adjusts to from a clear image of a distant one

Answer 16

cilliary muscles relax
suspensory ligaments tighten
lens get thinner
less light refraction
light rays less focused on retina

Question 17

explain why a long-sighted person has difficulty seeing near objects clearly (2)

Answer 17

eyeball is too short/ lens not thick enough
light focused behind retina

Question 18

explain why a short-sighted person has difficulty seeing distant objects clearly (2)

Answer 18

eyeball is too long/too thick
light focused in front of retina

Question 19

describe how lenses can correct long-sightedness (3)

Answer 19

convex lens
refracts light inwards
light ray focuses on retina

Question 20

describe how lenses can correct short-sightedness (3)

Answer 20

concave lens
refract light outwards
light ray focuses on retina

Question 21

describe the process of natural selection (5)

Answer 21

there is a genetic variation in the population
individuals with beneficial alle (refer to exam question)
these are more likely to survive
therefore more likely to breed
pass on beneficial alle to future generations

Question 22

describe how a natural selection leads to antibiotic resistance (5)

Answer 22

variation between the bacteria
a random mutation causes a bacteria to become resistant to anti-biotics
the resistant bacteria survives whereas non-resistant bacteria are killed by antibiotics
antibiotic resistant allele passed on
population of resistant strain of bacteria increases

Question 23

use lamarks theory to explain how an organisms characteristics evolve (eg. longer neck in giraffes) (2)

Answer 23

used characteristic more in its lifetime (eg. stretched to get food)
trait passed on to offspring

Question 24

describe the process of selective breeding (5)

Answer 24

organisms with desired trait is selected
organism with second desired trait is selected
breed two organisms together
select offspring with both traits and breed again
repeat for many generations

Question 25

describe the process of speciation (6)

Answer 25

variation in the population population gets geographically isolated there is different environmental factors in each area natural selection occurs and the best adapted individuals in each location survive and reproduce different alleles are passed on in each population populations can no longer interbreed to from fertile offspring-therefore have formed a new species

Question 26

describe how a fossil is formed in rock (4)

Answer 26

organism dies and gets buried in sediment soft parts of organism decay hard parts (bones/shell) do not decay bones get replaced with minerals

Question 27

random sampling method (6)

Answer 27

lay two tape measures to make a grid get random co-ordinates using a random number generator place quadrat at co-ordinates and count individuals repeat to get 20 samples calculate mean number of individuals estimate size of population by doing: mean number of individuals x area

Question 28

transect sampling method (5)

Answer 28

use a random number generator to randomly lay a tape measure in a straight line place a quadrat next to the transect and count number of individuals repeat every 2m along the transect repeat this transect in another random location compare data

Question 29

describe how water content is controlled when water content of blood too high (3)

Answer 29

small volume of concentrated urine is formed no ADH released less water reabsorbed into blood