Paper 2 Flashcards
Homeostasis
An organisms ability to regulate its internal conditions so crucial reactions can occur at optimal rates
What needs to be regulated in the body?
Blood glucose concentration
Internal temperature
Water levels
Explain how reflex actions work
- Receptor in the skin detects a stimulus
- Sensory neurone sends electrical impulses to relay neurone, which are located in the spinal cord. They connect sensory neurones to motor neurones.
- signals travel across synapses via neurotransmitter chemical
- Motor neurone sends electrical impulses to an effector.
- Effector produces a response
How do glands work as effectors?
They secrete chemicals
Reaction time practical
- drop ruler between finger and thumb
- measure distance fallen before caught- repeat, find a mean
- independent variable- stimulant increases neurotransmission, depressant decreases neurotransmission
Cerebral cortex
Front of brain
Higher functions
Memory, speech, problem solving
Cerebellum
Back
Motor skills
Movement, balance, coordination
Medulla oblongata
Stick at back of brain
Unconscious activity
Heart and breathing rate, signals to adrenal glands to release adrenaline
What allows doctors to see brain activity?
MRI scans
What happens to focus on near objects?
Ciliary muscles contract
Suspensory ligaments loosen
Lens thickens
What happens to focus on a distant object?
Ciliary muscles relax
Suspensory ligaments tighten
Lens is thinner
what do rods detect
light intensity
what are cones sensitive to
red, blue or green wavelengths of light
myopia
short sightedness
hyperopia
long sightedness
treatments for eyesight
glasses, contact lenses, laser eye surgery, lens replacement
how does thermoregulation work?
brain detects blood temperature then sends nervous and hormonal signals to effectors
how does the body respond to being too hot?
sweat glands produce water which evaporates, removing heat
blood vessels widen- vasodilation- increases blood flow to skin, increases rate of heat loss
how does the body respond to being too cold?
hairs stand on end to trap air
shivering- muscles produce more heat
blood vessels contract- vasoconstriction - decreases blood flow to skin, decreasing rate of heat loss
endocrine system
system of glands that secrete hormones to send signals to effectors, transported via blood which is slower than the nervous system
pituitary gland
“master” gland which sends signals to other glands
pancreas
produces insulin and glucagon to control blood sugar
testes
produces sperm
ovaries
release eggs and secrete hormones
adrenal glands
release adrenaline
thyroid
controls growth and metabolism
what happens when blood glucose is too high
pancreas secretes insulin, causes glucose to move from bloodstream into cells which can then be used for respiration and excess glucose is converted into glycogen as energy store
what happens when blood glucose is too low?
pancreas secretes glucagon, causing liver and muscles to convert glycogen back into glucose
T/F? controlling blood glucose is an example of negative feedback
True
how is type 1 diabetes caused
pancreas cannot make enough insulin
how is type 2 diabetes caused
cells do not absorb glucose as they should
how is water lost in the body
through exhalation, sweating and urinating
if blood is too concentrated (cells)
- water lost by osmosis
-flaccid
if blood is too dilute (cells)
- water gained by osmosis
- cell turgid/ will explode
selective reabsorption
blood passes through capillaries where small molecules are filtered out of the blood (urea, ions, water, glucose). These pass into tubes and all the glucose, and some ions and water are reabsorbed
Deamination
When we digest protein, amino acids pass into the blood but we often eat more than enough protein so the liver breaks down excess amino acids and produces ammonia
Why is ammonia converted into urea
It’s toxic
Water is mixed with urea to make
Urine
If blood is too concentrated, ADH from pituitary gland causes tubules in kidneys to
Reabsorb more water into bloodstream – less urine
If water level is too high-
(Kidneys)
Less ADH made, less water reabsorbed so more water is sent to the bladder to leave body as urine
What’s kidney failure
Where kidneys contain a higher concentration of water, ions and urea than it should
How does dialysis work
- patients blood passes over a partially permeable membrane, allowing small molecules through but not larger ones such as proteins
- on the other side of the membrane is the dialysis fluid which contains the normal concentration of water and ions but no urea
- the urea diffuses from blood into dialysis fluid
- the fluid is constantly refreshed so there’s always a high concentration gradient for urea
- normal concentration of ions and water
How does a kidney transplant work
Diseased kidney is replaced by a healthy one from a donor, but there’s risk of rejection
LH
- produced by pituitary gland
- causes egg to be released, which travels towards uterus
- sperm can fertilise it in oviduct
Progesterone
- produced by ovaries
- maintains uterus lining
Contraception
FSH inhibiting pill
Progesterone injection/implant
Condom/diaphragm
IUD (copper coil)
Avoiding sex for time after egg release
Clamping oviduct or vasectomy (cutting sperm tubes)
FSH inhibiting pills
No eggs mature
Progesterone injection/implant
Stops eggs being released
Condom/diaphragm
Stop sperm entering vagina
IUD (copper coil)
Stops egg embedding in lining
How can not enough FSH or LH be treated
Injections
How does IVF work?
Eggs collected after inducing release with LH to be fertilised in a lab, and embryos then inserted back into uterus
What do adrenal glands do and where are they?
- top of the kidneys
- release adrenaline which increases blood flow and breathing rate, to prepare for fight or flight
What’s phototropism?
Auxin gathers on shaded side of a plant so those cells elongate, causing the shoot to bend towards the sun
What does ethene do in plants?
Causes ripening
What does gibberellins do?
- induces germination
- promotes flowering
- increases fruit size
Transplant pros and cons
Pros- patients can lead normal life, only initially expensive
Cons- shortage of donors, risk of rejection, have to take drugs forever
Dialysis pros and cons
Pros- no shortage
Cons- frequent treatment, control diet, expensive long term
FSH
- from pituitary gland
- causes an egg to mature
- stimulates oestrogen production
Oestrogen
- produced by ovaries
- inhibits FSH, so no more eggs mature
- causes uterus lining to thicken
- stimulates LH production
Problems with IVF
- low success rate
- risk of there being more than one embryo
What does the thyroid do?
- secretes thyroxine which controls metabolic rate and controls growth
What happens if not enough thyroxine is being secreted?
Hypothalamus releases TRH, causing pituitary gland to release TSH, causing thyroid to release more thyroxine
Geotropism
Auxin gathers on the bottom of roots where it inhibits growth, so roots grow downwards
Auxin practical
- place seeds on damp cotton wool in a petri dish, stand it on its side
- after a few days, rotate it - the roots will have bent
What can auxins be used for?
- weedkillers, rooting powders, promoting growth in tissue cultures
Meiosis - definition
Process by which gametes are made which are genetically different from parent cells
Where does meiosis occur in humans
Testes or ovaries
What are the stages of meiosis?
- Chromosomes are copied
- Cell divides into 2
- Cell divides again, so there are 4 genetically different gametes from 1 cell- each with different alleles
How can animals reproduce
Sexually
How can plants reproduce
Sexually or asexually
Asexual reproduction
Happens by mitosis
Produces an identical daughter cell
Sexual reproduction
Consists of both mitosis and meiosis
Offspring’s inherits 50% from each parent
Genetical variation
Advantages of sexual reproduction
Offspring better adapted to different environments because of variation
Advantages of asexual reproduction
- 1 organism is needed to reproduce
Genome
Entire genetic code in an organism
DNA
Double helix polymer- stores genetic code
Gene
Portion of DNA, codes for a protein
Genotype
Organisms specific genetic code
Phenotype
Physical characteristics
Monomers between DNA strands are called— and are made from—-
Nucleotides, sugar/ phosphate group
Base pairings in DNA
A and T
C and G
Every ___ bases codes for ___
3, an amino acid
Proteinsynthesis
Code is copied by mRNA, taken to ribosome which assembles amino acids into polypeptides then proteins that are folded into shape
Mutations can result in
Wrong proteins being synthesised
Characteristics are determined by
The type and quantity of proteins synthesised
Some characteristics are controlled by 1 gene, tho most are the result of
2 or more
Allele
Different versions of the same gene
Dominant allele
Expressed as (ie. Bb or BB) - at least 1 cap
Recessive allele
Expressed as (ie. bb) - all lower case
Homozygous
Two of the same - ie BB or bb
Heterozygous
One of each - Bb
XX chromosomes
Femaleb
XY chromosomes
Male
Darwins theory
Random mutations result in variation
Some organisms are better suited to environment
These compete - survival of the fittest
Those better adapted are likely to survive and reproduce, passing on the allele
Lamarcks theory
Mutations are a result of environment affecting characteristics, inherited by offspring
Antibiotic resistant bacteria are evidence for what? How?b
Darwin theory of evolution
- if not all bacteria are killed, the most resistance reproduce
Genetic engineering
Inserting a gene into an organisms genome so it synthesises a specific protein to achieve a desired characteristic, ie insulin producing bacteria, disease resistant crops
Species
If the same species, two organisms can produce fertile offspring
Selective breeding
Breeding organisms that have desired characteristics to produce offspring in which they are more pronounced
Process of genetic engineering
- Desired gene cut from another organism’s DNA using an enzyme
- Gene inserted into a vector (bacteria plasmid or virus)
- Vector inserts gene into cells of another organism early in development
- Organism develops with desired characteristic
Fossils
Decayed remains of organisms
How are fossils formed?
- parts of undecayed organisms- because conditions for decay aren’t present
- when parts of the organism are replaced by minerals
- preserved traces
Cloning
Producing genetically identical organisms
Methods of plant cloning
- tissue cultures
- cuttings
Cloning process
- Nucleus taken from skin cell of organism to be cloned
- Nucleus inserted into an egg cell
- Electric shock causes cell to split and develop
- Developing cells inserted into surrogate mother
- Clone born
Classification system
Kingdom, phylum, class, order, family, genus, species
An organism’s binomial name is made from
Genus + species
3 domains: (with examples)
Archaea (extremophiles)
Bacteria (true bacteria)
Eukaryota (anything with DNA in the nucleus- ie plants and animals)
What do organisms compete for
O2
CO2
Water
Food
Space
Mates
Light
Interdependence
Organisms depending on each other for survival, forming a community
Abiotic factors
Non living factors- ie O2, CO2, light, temp
Biotic factors
Impact of other organisms on an ecosystem ie predators, pathogens
Quadrat practical
- place quadrat in random positions in an area
- count number of chosen organisms in each, calculate a mean then multiply by total area to get population estimate
- moving along a transect allows you to observe changes in a population density over a distance- ie how light intensity effects biodiversity
What do food chains show?
Direction of energy transfer between organisms
Producers
- produce biomass
- get energy from the sun
Primary consumer
Herbivores/omnivores
Secondary consumers
Carnivores/omnivores
Tertiary consumers
Carnivores/omnivores
Apex predators
Top of the chain, no natural predators
Biodiversity
Variety of species of organisms that exist in an ecosystem
Why does a high biodiversity ensure a stable ecosystem?
Organisms will be able to be dependant on a greater number of other species for survival
Why does human development reduce biodiversity?
Destroyed habitats, disposed waste
How is land used by humans
- Quarrying
- Building
- Farming
- Disposing waste
What’s the deal with peat bogs?
- they’re destroyed in order to make compost
- destroying them reduces biodiversity, and releases CO2
What do pyramids of biomass indicate?
How much biomass is transferred between trophic levels
Why is biomass lost at each trophic level?
- not all consumed or absorbed
- excreted in faeces
- lost in respiration
Food security factors
Changing diets/growing environments/conflict/fuel and energy prices/cost of farming
Why are farmers trying to farm more efficiently?
To increase biomass input and reduce wasted biomass
Sustainable fishing ensures…
(+ example)
- fish aren’t caught faster than they can breed
- nets with large holes so young fish can escape and breed
- fishing bans during breeding season
What’s the purpose of GM crops?
Can increase yields
Cornea
Refracts light as it enters the eye
Iris
Controls how much light enters the pupil
Lens
Further refracts light to focus it onto the retina
Retina
Contains light receptors
Optic nerve
Carries impulse from eye to brain
Sclera
Tough white outer layer of eye to protect from injury
Food security
Having enough food to feed a population
Why does deforestation occur
Provide land for cattle and rice fields
Grow crops for biofuels
Deforestation pros
- allows humans to obtain useful resources and grow food
- provides economic benefits and jobs
Deforestation cons
- reduces biodiversity
- increases risk of drought and flooding
- less CO2 removed from the atmosphere, contributing to global warming
- burning trees releases CO2
How to write about Darwins theory
- variation
- environmental change
- suited/ survive
- reproduce
- allele
- generation
- population
Tissue culture
Using small groups of cells from a plant to grow identical new plants. This is important for preserving rare plant species or commercially in nurseries
Cuttings
Taking a section of plant and planting it directly into new soil using hormones to stimulate new root growth
Stimulus
Change in the internal or external environment
Receptors
Cell that detects stimulus
Coordination centre
Receives and processes information from receptors
Central nervous system
Brain and spinal cord
Effector
Muscle or gland that brings about a response
Neurone
Specialised cell that carries an electrical impulse
Milk RP
- place fresh milk into 3 beakers
- keep each beaker at a different temperature
- use an indicator to measure pH of each beaker after different time periods
Carbon cycle
All living material is carbon-based.
Carbon is cycled between living tissue, dead tissue and the Earth’s atmosphere
Decomposers
Recycling useful minerals such as nitrates and carbon dioxide by breaking down dead or decaying organisms
Water cycle
Provides fresh water for plants and animals on land, before draining into the sea
how do you find percentage loss?
(larger number- smaller number)// larger number)) x100
how do you find total population size?
(total area// area sampled) x number of organisms of that species counted in sample
bioaccumulation
occurs when toxins build up - or accumulate - in a food chain. The animals at the top of the food chain are affected most severely.
eutrophication
- Sewage or fertiliser run-off increases the nutrient concentration of the water.
- Extra nutrients cause increased growth of the aquatic plants/algae – this is known as an algal bloom.
- The algal bloom covers the water’s surface killing any plants below the surface as light and oxygen cannot reach them.
- Algae also die as the nutrients run out.
- Aerobic bacteria decompose the dead plants.
- Bacteria use up oxygen for
respiration - Fish and other organisms die from a lack of oxygen.
problems with selective breeding
- inbreeding - breeding closely related animals or plants
- this can cause disease or for them to have inherited defects
how does selective breeding work?
- select the male and female with desired characteristics and breed them together
- From the offspring, select the male and female with desired characteristics and breed them together
- Keep repeating this over generations, until all offspring have desired characteristic
