Paper 2 Flashcards
Homeostasis and Response, Inheritance, Variation and Evolution, Ecology
What is the function of the cerebral cortex
consciousness, intelligence, memory, language
What is the function of the cerebellum
coordinates muscle activity
What is the function of the medulla
unconscious activity
How does an electrical impulse pass between two neurones
- synapse
- chemical released into the gap
- chemicals attach to the next neurone and set up a new electrical impulse
- diffuses across the gap between the 2 synapses
What is the iris
coloured part of the eye
contains muscles that control size of pupil
what is the retina
layer of receptors at the back of the eye containing light sensitive cells (rods and cones)
what is the ciliary muscle
contracts and relaxes to control shape of the lens
what are the suspendory ligaments
tighten and slacken to change shape of lens
what is the lens
sits behind pupil and focuses light on the retina
What happens in order to focus on a near object
- ciliary muscles contract
- suspensory ligaments loosen
- lens becomes thicker/more curved so refracts light rays more strongly
What happens in order to focus on a far object
- ciliary muscles relax
- suspensory ligaments tighten
- lens becomes thinner/flatter so refracts light rays slightly
What is myopia and how can it be corrected
short sightedness - far objects are blurred
light focuses in front of the retina
concave lens
What is hyperopia and how can it be corrected
long sightedness - near objects are blurred
light focuses behind the retina
convex lens
What happens in dim light to the eye
radial muscles contract
pupil dilates
what happens to the eye in bright light
circular muscles contract
pupil contracts
Can you define homeostasis?
The maintenance of a constant internal state!
What happens when the core body temperature is too high?
- change detected by thermoregulatory centre in the brain by blood flowing around brain
- Vasodilation to increase rate of heat loss because it allows more blood to flow through the skin
- sweating
- The sweat evaporates, transferring heat energy from the skin to the environment
What happens when the core body temperature is too low?
- change detected by thermoregulatory centre in the brain by blood flowing around brain
- skeletal muscles contract and relax rapidly and we shiver.
- These contractions need energy from respiration, and some of this is released as heat
- Vasoconstriction to reduce heat loss - allows less blood to flow through the skin and conserve the core body temperature
- Hair erector muscles contract and our hair stands on end, trapping a layer of air beneath it to insulate us
What happens in the body when blood glucose levels are too high
-insulin is released from pancreas
-glucose moves from blood into cells
-excess glucose is converted to glycogen in the liver and muscle cells for storage
What happens in the body when blood glucose levels are too low
-glucagon is released from pancreas
-glycogen converte to glucose and released into blood
-amino acids/fats are broken down
What happens when water concentration in the blood is too high
-Less ADH released from pituitary gland
-kidney tubules reabsorb less water
-more (dilute) urine produced (higher conc of water)
What happens when water concentration in the blood is too low
-More ADH released from pituitary gland
-kidney tubules reabsorb more water
-less urine produced (lower conc of water)
How does your body get rid of proteins
- broken down into amino acids
- deaminates them in liver
- forms ammonia which is toxic
- converted into urea (also toxic) which can be excreted safely from the body
- the rest of the amino acid molecule can be used for respiration or to make other molecules
Describe the process of kidney dialysis
- blood is temporarily removed from the patients body
- this is filtered through a dialysis machine
- the patients bood passes over dialysis fluid
- the dialysis fluid has no urea
- urea/waste products diffuse from high concentration in patient’s body to low concentration in fluid
- patient’s blood is returned to their body
What is the use of adrenaline
-preparesbody for fight or flight
-increases heart rate
-increases delivery of oxygen and glucose to brain and muscles
-does not involve negative feedback and is secreted from the adrenal glands
Describe FSH
-released by pituitary gland
-causes eggs to mature in ovaries
-stimulates ovaries to produce oestrogen
Describe LH
-released by pituitary gland
-stimulates release of mature eggs from ovaries (ovulation) around day 14 of the cycle
Describe oestrogen
-released by ovaries
-causes lining of uterus to thicken and grow
-inhibits release of FSH
-stimulates release of LH
Describe progesterone
-released by ovaries
-maintains lining of the uterus
-inhibits FSH and LH
explain the process of IVF
- mother given FSH and LH to stimulate maturation of several eggs
-eggs are collected from mother and fertilised by sperm from father
-fertilised eggs develop into embryos
-multiple embryos are inserted into mother’s uterus
what are the disadvantages of fertility treatment?
- emotionally and physically stressful
-low success rate
-can lead to multiple births which put the mother and babies at risk
What are auxins
- plant growth regulator hormone
- unequal distibution can be seen in phototrophic reactions, causes unequal growth/leaning
Uses as: - weedkiller
-rooting powder
-promoting growth in tissue cultures
What is ethene
- hormone that controls ripening and cell division in plants
Uses as: - controlling ripening of fruit during storage and transport
What are gibberellins
-regulates developmental processes such as seed germination
Uses:
-end seed dormancy
-promote flowering
-increase fruit size
Describe adult cell cloning
-The nucleus is removed from an unfertilised egg cell
-The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
-A very small electric shock stimulates the egg cell to divide (by mitosis) to form an embryo
-These embryo cells contain the same genetic information as the adult skin cell
-When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female (known as the surrogate mother) to continue its development until birth
-Offspring is a clone of original animal
Describe embryo cloning
-Egg cells from the best cow are artificially fertilised using sperm cells taken from the best bull
-This forms an embryo
-The developing animal embryo is then split apart many times before the cells of the embryo become specialised
-This forms many separate embryos that are genetically identical
-These cloned embryos are then transplanted into host mothers
-The calves born from these host mothers are all genetically identical
What are the advantages of cloning
-Preserve endangered species of plants and animals
-Quickly and cheaply produce commerical quantities of high quality plants year round
What are the disadvantages of cloning
-population are genetically similar so are susceptable to disease
-cloned animals are often malformed/have injuries/bad health
-ethics
Explain the process of selective breeding
- choose parents with desired characteristics
-breed
-choose offspring with desired characteristics and breed
-continue over many generations until all offspring show desired characteristic - can lead to inbreeding
- reduces variation in population
Describe tissue culture
-Cells are scraped from the parent plant (these cells are known as explants)
-The cells are transferred to a sterile petri dish containing nutrient agar
-Hormones (eg. auxins) are added to encourage plants to grow into small masses of tissue (callus tissue)
-Tissue continues to grow and forms plantlets that can be transferred to individual potting trays and develop into plants
Describe cuttings
-An older and more simple method to clone plants (mainly used by gardeners) is by taking cuttings
-Gardeners take cuttings from good parent plants (eg. those that are healthiest and best-looking) – a section of the parent plant with a new bud is cut off
-These cuttings are then planted and grow into genetically identical versions of the original plant
-Plants cloned by taking cuttings can be produced cheaply and quickly
Describe genetic modification
-enzymes cut out the desired gene from cell A from an organism
-vector taken out of cell B (usually bacterial plasmid or virus)
-gene is inserted into vector
-this is inserted into a cell - often for production is bacteria so binary fission can take place
-eg insulin collected and purified
-as organism grows, it develops with desired characteristics from gene
What are the benefits to genetic engineering
-potential to overcome inherited diseases
-GM crops can have higher yields - higher value crops
-crops can be engineered to be resistant to herbicides/produce own pesticide/drought resistant
what are the risks of genetic engineering
-genes fromGM plants/animals may spread into other wildlife and affect ecosystems
-ethical concerns - children
-GM crops are infertile and expensive to buy, not sustainable for smaller farmers/poorer countries to use
-some believe affects of GM have not been fully researched
what are the advantages of sexual reproduction
- produces variation in offspring
- offspring may have survival advantage by natural selection
what are the advantages of asexual reproduction
- only one parent needed
- time and energy efficient
- faster than sexual reproduction
- many identical offspring can be produced
- successfull traits are always passed on
what are the disadvantages of sexual reproduction
- finding a mate and reproducing is time consuming and requires lots of energy
- slow
what are the disadvantages of asexual reproduction
- reduced genetic variation, more susceptible to extinction by disease
- harmful mutations would be passed on
what is mitosis
the process of producing 2 identical body cells that contain 23 pairs of chromosomes
what is meiosis
the process of producing 4 non-identical gametes that contain 23 single chromosomes
Explain the process of meiosis
- each chromosome becomes shorter, thicker and more visible.
- the chromatids are joined at the centromere
- nuclear envelope disappears
- spindle fibres come out from each end of the cell and attach to the centronomes of the chromosome
- homologous chromosomes pair up in the centre of the cell
- small parts of the homologous chromosomes cross over. this exchange of genetic material increases variation
- the spindle fibres contract, separating the homologous pair into opposite sides of the cell, which begins to divide. each chromosome is still formed of 2 chromatids
- a new nuclear envelope forms aroud each set of chromosomes and the cell finishes dividing
- each cell has 23 chromosomes
- this happens again and 4 daughter cells are formed with 1 chromosome each, genetically different haploids
Describe reproduction in fungi
- some reproduce sexually when conditions are not good
- 2 hyphae from different fungi join and the nuclei fuse so the new hypha has 2 sets of chromosomes
- undergoes meiosis to make haploid spores, making them different from original hyphae
Describe reproduction in plants
- plants eg strawberry and spider plats have tiny new plants that form on the end of runners
- can reproduce sexually or asexually
Describe reproduction in malaria parasites
- reproduce differently in different life stages
- drop in temperature between human and mosquito triggers sexual reproduction
what is a gamete
a specialised sex cell formed by meiosis
what is a chromosome
long molecule found in the nucleus of cells formed by dna
what is a gene
part of a chromosome that codes for a protein
what is an allele
different forms of the same gene
what is a genotype
combination of alleles an individual has
what is a phenotype
physical expression of the genotype
what is DNA made of
a double helix, consisting of two strands of nucleotides
repeating nucleotide units
What is in a chromosome
DNA