Long Answer Questions Flashcards
What are the steps of mitosis
step 1) long uncoiled chromosomes not yet individualy visible
chromosomes are replicating
step 2) chromosomes shorten, thicken and replicate to form 2 i i
identical chromatids
chromosomes now visible
nuclear membrane disappears
step 3)chromosomes line up at equator of cell
spindle fibres attach to pairs of chromatids
step 4)pairs of chromatids are pulled apart and chromosomes are
pulled to opposite ends of the cell.
step 5) nuclear membrane reforms and cytoplasm divides.
step 6)two identical diploid cells are produced.
What are the steps of protiein synthesis
1) In Nucleus DNA unwinds and the strands separate.
2) mRNA creates a complimentary copy of the DNA code.
3) mRNA carries the code through the cytoplasm to a ribosome.
4) The order of mRNA bases determines the order of amino acids.
5) Amino acids join together to form a protein (joined by peptide bonds)
What are all the steps of photosynthesis
Stage 1 (Light reactions)
-Light energy from the sun is trapped by chlorophyll in the chloroplast.
-Light energy is converter into chemical energy which is used to make ATP.
-Water is split into oxygen and hydrogen, oxygen diffuses out of cell but hydrogen is retained for stage 2.
Stage 2 (Carbon Fixation)
A series of enzymes controlled reactions, which use hydrogen and ATP (from stage 1) with CO2 to produce glucose.
What are the steps of transpiration?
1) water enters a plant through the root hairs from the soil by a process of osmosis (water moves from a region higher water concentration in the soil to a region of LWC in the root hair)
2)Water then travels upwards through the xylem vessels.
3) The underside of leaves have small pores called Stomata. Water evaporates through the stomata into the air which creates a sucking action to draw the water upwards (against gravity).
This moves water from the roots to the top of the plant, without using energy.
How can fertilisers become an environmental issue?
-fertilisers can leach into freshwater, adding extra, unwanted nitrates.
-This will increase algal populations which can cause an algal bloom.
-Algal blooms reduce light levels, killing aquatic plants.
-These dead plants, as well as dead algae, become food for bacteria, which greatly increases populations.
-The bacteria use of large quantities of oxygen, reducing the oxygen availability for other organisms.
Describe the nitrogen cycle
-The chemical element nitrogen is important to living organisms because it is a component of all the different amino acids, that are used to make proteins.
-Nitrates dissolved in soil are absorbed into plants by their roots.
-Nitrates are used to produces amino acids, which are synthesised into plant proteins.
-Animals consume plants or other animals to obtain amino acids for protein synthesis.
- Fertilisers can be added to soil to increase the nitrate content of the soil
What is natural selection
Occurs when selection pressures are present in an environment, only the best adapted individuals survive and reproduce.
Natural selection increases the frequency of favourable alleles that present a selective advantage within the population.
“survival of the fittest organism”
Describe the stages of antibiotic resistance
1) One mutant bacteria arrives spontaneously within the population.
2) Mutant bacteria has a selective advantage against the antibiotic it is exposed to.
3) Mutant bacteria reproduces to make more resistant bacteria.
4) One of these mutant bacteria has a selective advantage against a second antibiotic that it is exposed to and survives.
5) Mutant bacteria reproduces to make more resistant bacteria
What are the stages of speciation?
Stage 1 - Isolation
Original population is separated into two sub-populations by an isolation barrier.
Stage 2 - Mutations
Random mutations arise within each sub-population which increases variation between organisms.
Stage 3 - Natural Selection
Each sub-population is exposed to different selection pressures. Only organism with a selective advantage survive and reproduce.
Stage 4 - Speciation
The gene pool of each sub-population changes over many populations. The organisms become so genetically different they can no longer interbreed to produce fertile offspring - therefore they are no longer of the same species.
What is natural selection?
Occurs when selection pressures are present in an environment, only the best adapted individuals survive and reproduce.
Natural selection increases the frequency of favourable alleles that present a selective advantage within the population.
