BIOLOGY PAPER 2 FROM PMT NOTES

What is homeostasis? What does it regulate?

homeostasis is a process needed to maintain constant internal conditions regardless of external environmental changes. mechanisms are in place to keep optimum conditions. This is needed for enzyme action and cell function. it regulates blood glucose concentration, body temperature and water levels

what do all control systems have and what do they do

receptors are cells that react to stimuli (changes in environment), coordination centres process the information given by the receptors, effectors respond to bring conditions in the body back to optimal levels. control systems detect changes and respond to them.

examples of coordination centres and effectors

CC - brain, spinal chord, pancreas E - muscles, glands

what types of communication are involved in control systems?

nervous, hormonal

what is the nervous system

the nervous system allows us to react to our surroundings and coordinate reactions in response to stimuli

what do receptor cells do

they convert stimuli into electrical impulses

where does the electrical impulse go?

it goes along cells called sensory neurons to the central nervous system

what happens at the central nervous system?

the electrical impulse is processed and a reaction is sent through motor neurons by an electrical impulse to the effectors

what do effectors do?

they carry out the response (e.g. muscles contracting, glands secreting hormones)

what are automatic responses and how do they happen

automatic responses are reflexes. they are important so that the body does not get hurt. the information is sent down the reflex arc, skipping the brain and going straight to the effector for an immediate response. the impulse does not pass through the conscious areas of the brain.

descrive the reflex arc thing

a stmulus is detected by receptors, the receptors send an impulse to the CNS through sensory neurons where the impulse is sent to a relay neuron. impulses are sent along a motor neuron to the effector to produce a response.

examples of reflex arcs?

pupil getting smaller to avoid damage from bright lights, moving your hand from a hot surface to prevent damage.

what is a synapse

synapses are gaps between neurons that when an impulse comes to the end of the first neuron, will release a chemical that diffusses across the synapse and reaches the second neuron to trigger another impulse to begin again in the next neuron. one door closes another one opens type shit. it gets to the end, the chemical goes to the next then another is born type shit.

what is reaction time and how can it be tested

your reaction time is the time it takes for you to respond to a stimulus. it can be measured with the ruler drop test

what is the endocrine system and what is it made up of

the endocrine system sends hormones around the body which produces responses when they reach certain tissues. it is made up of glands which secrete hormones directly into the bloodstream

what is pituitary gland

the master gland, it secretes hormones into the blood to have an effect on the body or act on other glands to stimulate them and produces different hormones

what is pancreas

secretes insulin to control blood glucose levels

what is thyroid

secretes thyroxine to control metabolic rate, heart rate and temperature

what is adrenal gland

secretes adrenaline when involved in fight or flight situations. body’s response to stressful situations

what is ovary

secretes oestrogen which is involved in the menstrual ctycle and development of female sexual characteristics (different features that develop during puberty that distinguish a female from a male)

what is testes

secretes testosterone and is involved in the production of sperm and the development of secondary male sexual characteristics

what does the blood do in the endocrine system

it transports the hormone to a target organ or tissue where it will have an effect

is the nervous or hormonal system faster?

hormonal system is much slower but it acts for longer

what does the pancreas do if there is a high blood glucose level

the pancrease secretes insulin which makes the blood in the bloodstream to move to cells to perform respiration. excess glucose is turned into glycogen as an energy store

what does the pancreas do if there is a low blood glucose level

pancrease secretes glucagon which makes the liver and muscles turn glycogen back into glucose

explain type 1 diabetes

pancrease cannot produce enough insulin, injections are needed

explain type 2 diabetes

cells do not absorb glucose as they should, obesity increases the chance of type 2 developing

what are the primary reproductive cells in females

females are born with eggs which start to mature during puberty

What does follicle stimulating hormone do?

FSH is secreted by the pituitary gland and causes an egg to mature and the ovaries to produce oestrogen

what does oestrogen do

oestrogen causes the uterus lining to thicken and it stops FSH to prevent another egg from maturing until the next cycle. it also causes the pituitary gland to secrete luteinising hormone

what does the luteinising hormone do

luteinising hormone causes eggs to be released which travel towards the uterus where a sperm cell can feritlise it if in the oviduct

what is progesterone

hormone that is secreted by the ovaries thickening the uterus lining

examples of contraception and what each do

FSH-inhibiting pills - no eggs will mature

progesterone injection or implant - stops eggs from being released

condom/diaphragm - stops sperm from entering the vagina

IUD (copper coil) stops eggs from embedding in the lining

celibate - avoiding sex for a time after an egg is released

clamping oviduct or vasectomy (cutting sperm tubes)

fertility treatments

not enough FSH/LH - injections

explain IVF

IVF - in-vitro fertilisation - eggs are harvested from the woman after inducing the release with LH to be fertilised in a lab with the father’s sperm. any viable embryos that are grown are inserted back into the uterus which hopefully embed into the lining and grow normally. success rate is very low, can potentially cause mutliple embryos to develop

what gland releases adrenaline and what does adrenaline do?

the adrenal gland attack to the top of your kidneys release adrenaline which increase blood flow and breathing rate when the body is involved in flight or fight situations, stress.

what gland releases thyroxine and what does thyroxine do?

the thyroid releases thyroxine which controls the body’s metabolic rate. if thyroxine levels are too low, the hypothalamus in the brain releases TRH which causes the pituitary gland (master gland) to release TSH which increases the production of thyroxine

what is the process that creates gametes

meiosis is the process by which gametes (sex cells like sperm and eggs) are made. the daughter cells are genetically different from parent cells

explain the meiosis cycle

the chromosomes in the diploid cell are copied, similar chromosomes pair up and the genes are swapped between them. the cell divides to produce 2 diploid cells. the cells divide further to produce 4 haploid cells (gametes)

how do plants reproduce sexually and what is one advantage of this

plants reproduce sexually through the process of pollenation and fertilisation to produce seeds. One advantage of this is genetic variation meaning the plant’s offspring may become better adapted to its environment

how do plants reproduce asexually and what is one advantage of this

plants reproduce sexually with mitosis meaning the daughter plants will be genetically identical to the parent plant. one advantage of this is that only one plant is needed to reproduce

what is genome

genome is the entire genetic code in an organism

what is DNA

double helix polymer that stores genetic code

what is gene

a portion of dna that codes for specific proteins and determines traits in an organism.

what is genotype

an organisms specific genetic code

what is phenotype

phenotypes are how genotypes are expressed physically and observable traits of an organism, influenced by both genetics and environment.

what are characteristics determined by? what are they controlled by and what are some a result of.

characteristics are determined by the type and quantity of proteins synthesised. some are controlled by one gene however most are controlled by two or more genes interacting with each other

what are alleles

alleles are different version of the same gene

explain dominant and recessive alleles

dominant alleles are expressed even when there is a recessive allele present. there must be 0 dominant alleles for a recessive allele to be expressed in the phenotype

explain homozygous and heterozygous

homozygous - bb BB

heterozygous - Bb

what is polydactyly caused by, what is cystic fibrosis caused by

dominant allele, recessive allele respectively

what are the chromosomes for female and male

XX - female

XY - male

what is genetic engineering

the insertion of a gene into an organisms genome to synthesise specific proteins to give the organism a desired characteristic/trait

e.g. insulin-producing bacteria for diabetes

what is the process of genetic engineering

the desired gene is cut from another organism’s dna with enzymes, the gene is inserted into a vector (bacteria plasmid or virus), the vector inserts the gene into cells of another organism in the early stages of development, organism develops with desired characteristic due to every cell synthesising the specific protein

what are fossils

the decayed remains of organisms that have died a long time ago

fossils that look like bones are actually minerals that have replaced the place where the bones were

some fossils can still have soft organic tissue if the requirements for decay are not prsent

footprints that have hardened in mud are also considered fossils as they show evidence of a species

what is linnaeus’s taxonomy?

(Domain), Kingdom, Phylum, Class, Order, Family, Genus, Species.

D (the) KPC OF GS if u forget

how are binomial names written

genus + species

Dorcus titanus

what are the three domains

archaea (primitive bacteria, extremophiles (live in extremem conditions). single celled microorganisms but are chemically and genetically different to bacteria, no peptidoglycan)

bacteria (true/normal bacteria. cell walls do have peptidoglycan, found everywhere, good and bad bacteria)

eukaryota (everything else - dna contained in nucleus)

what do organisms compete for?

food, water, o2, co2, mating, space, light

what is interdependence and what does it form

interdependence is organisms depending on one another for survival. when this happens, a community is formed.

abiotic factors?

non living factors including light, temperature, moisture, soil pH, CO2 and O2 concentration

biotic factors?

the impact of other organisms on an ecosystem, cows trampling plants - predators, prey and pathogens

explain how to sample / transect thing

place quadrat in random positions in the area (ideally 10% of the area, placed using a random number generator). count the number of chosen organisms in each, calculate the mean then multiply by the total area to get the estimate for population. moving it along a transect allows you to observe changes in population density over a distance

food chain

shows the direction of biomass transfer between organisms.

producers produces biomass. e.g. plants, algae. primary consumer herbivore/omnivore consume the producers, secondary consumers carnivore/omnivores consume the primary consumers. tertiary consumers consume the secondary consumer and can be carnivore/omnivore

apex predators are always at the top of the food chain and have no natural predator

all of these positions in the food chain are called trophic levels, and their population will fluctuate over time

carbon cycle

all life is carbon-based. when an organism dies and decomposes, the carbon is recycled. same when the organism is living as they excrete CO2. bacteria also secrete CO2

water cycle

rain falls and runs into rivers into the sea then it evaporates and the cycle continues

precipitation → travel across rivers into the sea → evaporation

biodiversity

the variety of organisms that exist in an ecosystem

high biodiversity does waht?

makes for a stable ecosystem as organisms have more organisms to depend on for survival rather than fewer

what does human development do to biodiversity

it decreases biodiversity due to destruction of habitats, disposing of waste in safe ways is getting harder (air pollution, toxic chemicals), so its harder to reduce our impact

explain the land aspect of human development and its impact on the environment

peat bogs are being destroyed to make compost. this reduces the biodiversity of that ecosystem, especially for microorganisms. burning peat releases CO2, contributing to global warming

deforestation also reduces biodiversity and is usually done to create farmland

explain the pyramid of biomass and the exchanges

Term

pyramid of biomass shows how much biomass is transferred between trophic levels % absorbed = above level / below level. any % = the bit / the lot x 100.

some biomass is lost at each level due to not all of the biomass being consumed/absorbed, organisms can lose biomass through excretion while they are alive.

explain food security

food security is becoming a big concern recently due to fuel and energy prices, chaning diets, growing environments, cost of farming and conflicts (wheat - ukraine but war)

farmers are trying to farm more efficiently by increasing biomass input while reducing wasted biomass

sustainable fishing?

if fish are caught at a faster rate than they are breeding, then eventually the fish can disappear in those areas. sustainable fishing ensures that fish are not caught before they have had time to reproduce so the population stays constant. an example of this could be to use a net with large holes to allow smaller (child) fish to escape and breed while some adult fish are caught

genetically modifying crops

can increase yields and other methods are being developed to provide nutrients - fungi grown on glucose syrup or making plants resistant to certain diseases so that they can grow normally and provide food / biomass