4B Diversity classification and variation Flashcards
what are gametes
sperm cells in males and the egg cells in females
when gametes join together in fertilisation what do they form
zygote, which divides and develops into a new organism
what diploid number to normal body cells have
2n
meaning each cell has two of each chromosome one from mum and one from dad
what is gametes haploid number
n
one copy of each chromosome
what happens at fertilisation
a haploid sperm fuses with a haploid egg making cell with normal diploid number
half chromosomes from mum (egg) and half from dad(sperm)
how is genetic diversity increased within species by fertilisation
fertilisation is random (any sperm with any egg(
so produces zygotes with different combinations of chromosomes to both parents (mixes genetic material)
where does meiosis take place
reproductive organs
how do cells start and finish via meiosis
start as diploid finish as haploids (have half the chromosomes)
6 steps of meiosis
1) before meiosis-DNA unravels & replicates so there are two copies of each chromosomes called chromatids
2) DNA condenses forming double armed chromosomes, made from two sister chromatids - sister chromatids joined by centromere
3) meiosis I- chromosomes orange into homologous pairs
4) homologous pairs separated halting chromosome number
5) meiosis II- pairs of sister chromosatids which make up each chromosome are separated (centromere divides)
6) four haploid cells(gametes) that are genetically different are formed
how many homologous pairs do human have
23
46 single chromosomes
during meiosis I what happens which causes the chromatids to have a different combination of alleles
homologous pairs of chromosomes pair up together
chromatids twist around each other and parts of the chromatids swap over
now chromatids still have same genes but different combination of alleles
how does the crossing over of chromatids during meiosis I produce cells which are genetically different
causes each of the four daughter cells formed have chromatids with different alleles
increases genetic variation
how does the independent segregation of chromosomes cause cells to be produced which are genetically different
when homologous pairs are separated (meiosis I) its random which chromosome from the pair ends up with which daughter cell
so 4 daughter cells have different combinations of those maternal and paternal chromosomes
this shuffling causes genetic variation in potential offspring
difference between meiosis and mitosis
1)mitosis produces cells w/same no. of chromosomes as parent cells
meiosis produces cells w/half chromosomes as parent cells
2)mitosis daughter cells are genetically identical to each other &parent cells
meiosis daughter cells are genetically different to each other and parent cell
3)mitosis produces two daughter cells
meiosis produces four daughter cells
how are chromosome mutations caused generally
errors in cell division
what is the chromosome mutation non-disjunction
failure of chromosomes to separate properly
what does non-disjunction of chromosome 21 cause
downs syndrome
detail how downs syndrome is caused
person having extra copy of chromosome 21
non disjunction means chromosome 21 fails to separate properly in meiosis so one cell gets an extra copy of chromosome 21 and the other cell gets none
so when the gamete with an extra chromosome fuses with another gamete at fertilisation the zygote will end up with 3 chromosomes 21
what is another mutation
changes to the base sequence of DNA
deletion or substitution
what is deletion mutation
one base is deleted (in DNA)
what is substitution mutation
one base is substituted with another (in dna)
how can a change in dna bases cause a mutation
as order of dna bases determines order of amino acids and therefore the protein which is made,
if the bases change the sequence of amino acids change and therefore a different protein is coded for
why do not all mutations affect the order of amino acids
substitution
as the genetic code is degenerate and more than one dna triplet can code for an amino acid
this mean substitution does not always result in change in amino acid sequence
why does deletion always cause change in amino acid sequence
as when a base is deleted it changes the number of base present - this causes a shift in all the base triplets after it
what are mutagenic agents
things that increase rate of mutations
examples of mutagenic agents
ultraviolet radiation
ionising radiation
some chemicals and viruses
how can gentic diversity within a population be increased
- mutations in DNA
- different alleles introduced into population
what is gene flow
when individuals from another population migrate into them and reproduce -causing genetic diversity increases
what is a genetic bottleneck
an event which causes a big reduction in a population
how do genetic bottlenecks cause reduction in genetic diversity
the reduction in population causes number of different alleles to reduce in the gene pool so reduces genetic diversity
what is the founder effect
type of genetic bottleneck
when a few organisms start new colony with only small number of alleles in gene pool
a gene which is rare in initial population may be very common in new colony
my lead to higher chance of genetic disease
how does founder effect normally occur
result of migration leading to geographical seperation
colony operates from original population for religion
example of founder effect
the amish
what is behavioural adaptations
ways an organism acts that increases chance of survival and reproduction
what is physiological adaptations
processes inside an organisms body which increase chance of survival
what are anatomical adaptations
structural features of an organisms body which increase chance of survival
what is directional selection
where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce
example of directional selection
bacteria evolving antibiotic resistance
what is stabilising selection
where individuals with alleles for the characteristics towards the middle of the range are more likely to survive and reproduce
what’s an example of stabilising slection
human birth weight -larger and smaller baby less likely to survive birth
what is phylogeny and what can it tell us
study of evolutionary history of groups of organisms
tells us who’s related to whom and how closely they are related
what is taxonomy
science of classification and names organisms organising them into groups
what does heriachy mean
groups organised into largest groups at top and smallest at Bottom
no overlapping groups
what are the three domains
eukarya
bacteria
archaea
what are the eight taxons
domain kingdom phylum class order family genus species
what is a species
group of similar organisms able to reproduce and give fertile offspring
what is the binomial system
nomenclature for classification
given one internationally accepted name in latin with two parts
what are the fist and second parts of names in classification called
genus is first
species is second
what is courtship behaviour
carried out by organisms to attract mate of right species
why is courtship behaviour species specific
prevents interbreeding
making reproduction more successful
explain genome sequencing
DNA base sequence of an organism can be compared to see how closely related they are
more closely related species will have a higher percentage of similarity in there base sequence
explain comparing amino acid sequence
related organisms have similar amino acid sequences in there proteins
what is cytochrome c
short protein found in many organisms
explain immunological comparisons
similar proteins bind to same antibodies
what is genetic diversity
the number of different alleles in a population
what can variation be caused by
genetic factors
environment
combination of genes and environment
why are samples used to study variation
as its too time consuming and impossible to be able to study a whole population
why do samples need to be random
make sure it accurately represents the population and makes sure it isn’t biased
could use random number generator
what is biodiversity
the variety of living organisms in an area
what is habitat
the place where an organism lives
what is community
all the populations of different species in a habitat
what local biodiversity
variety of species living in small habitats that’s local to you
what’s global biodiversity
variety of species on earth
greatest at the equator
what’s species richness
measure of number of different species in a community
how cam species richness/ biodiversity be worked out
take random samples of a community and count number of different species
what also effects the biodiversity number
the population size
big and small populations should not be treated the same way
what’s index of diversity
another way of measuring biodiversity
calculated with formula
higher number + more biodiversity
what can reduce biodiversity
agricultural practices
how can woodland clearance decrease biodiversity
decreases number of trees and tree species
destroys habitats and food resources
species may be forced to migrate or die
how can hedgerow removal decrease biodiversity
same reasons as woodland clearance
how can pesticides decrease biodiversity
chemicals kill pests that feed on crops
also reduces food resource
how can herbicides reduce biodiversity
chemicals kill unwanted plants
how can monoculture reduce diversity
farmers have fields which only contain one type of plant
what are some examples of conservation schemes which protect biodiversity
SSSI/ AONHb
environmental stewardship scheme
