diversity, classification and variation Flashcards
how is DNA passed from one generation to the next
gametes
what are gametes
sperm cells in males, egg cells in females,that join together during fertilisation to form a zygote
what does a zygote do
divides and develops to from a new organism
what do normal body cells have
diploid number of chromosomes
what does diploid mean
contains 2 of each chromosome, one from mother and one from father
what do gametes contain
haploid number
what does haploid mean
only one copy of each chromosome
what happens during fertilisation
haploid sperm fuses with haploid egg to produce diploid cell
how does fertilisation create genetic variation
it is random, so means zygotes with different combinations of chromosomes are produced
how are gametes formed
meiosis
what is meiosis
type of cell division that takes place in reproductive organs
what happens to diploid cells during meiosis
they become haploid
what happens before meiosis begins
DNA unravels and replicates, so there are 2 copies of each chromosome called chromatids, them the DNA condenses to form double-armed chromosomes each made from two sister chromatids
what are sister chromatids joined by
centromere
what happens during meiosis I (first division)
chromosomes arrange themselves into homologous pairs which are then seperated, halving the chromosome number
what are homologous pairs
chromosomes in the pair are the same size and have the same genes (but could have different versions of the genes)
what are different versions of the same gene called
alleles
what happens during meiosis II (second division)
the pairs of sister chromatids that make up each chromosome are seperated through the centromere dividing
what are produced from meiosis
4 haploid cells that are genetically different
what occurs during meiosis I
chromatids can cross over
what does chromatids crossing over produce
genetic variation
what occurs during the crossing over of chromatids
chromatids swap over and change alleles of the same gene
what does the crossing over mean for the 4 daughter cells produced
each cell has a different chromatid and so has a different set of alleles
what does independant segregation of chromosomes produce
genetic variation
what is independant segregation of chromosomes
when the chromosomes pair up randomly in meiosis I, leading to the 4 daughter cells having completely different combinations of the maternal and parental chromosomes
mitosis summary
produces 2 daughter cells with same number of chromosomes that are genetically identical
meiosis summary
produced 4 daughter cells with half number of chromosomes than parent cells that are genetically different
how many chromosomes do human cells
46, 23 pairs
what causes chromosome mutations
errors in cell division
what do chromosome mutations lead to
inherited conditions (as mutations are passed down through gametes)
examples of chromosome mutations
non-disjunction
what is non-disjunction
failure of chromosomes seperating properly
what can non-disjunction cause
downs syndrome
which chromosome causes downs syndrome
the failed seperation of chromosome 21 during meiosis leading to someome having an extra copy
what are mutations
changes to the base sequence of DNA
types of errors in the base sequence of DNA that leads to mutation
deletion or substitution of bases
what occurs during deletion of bases
one base is deleted
what occurs during substitution of bases
one base is substitutes with another (swapped)
do substitution of bases change the amino acid coded for
not always as some amino acids are coded for by more than one DNA triplet so the substitution could still code for the same amino acid
do deletion of bases change the amino acid coded for
yes as the triplets will shift, meaning all the amino acids coded for after the deletion will change
what are mutagenic agents
things that cause an increase in the rate of mutation
mutagenic agents examples
ultraviolet radiation, ionising radiation, some chemicals and some virus’
what is genetic diversity
number of different alleles of genes in a species or population
what increases genetic diversity within a population
mutations in the DNA following new alleles, different alleles being introduced into a population when individuals from another population migrate into them and reproduce
what is different alleles being introduced into a population when individuals from another population migrate into them and reproduce called
gene flow
what does genetic diversity allow to occur
natural selection
what is a genetic bottleneck
event that causes a big reduction in a population (e.g. death before reproduction)
what does a genetic bottleneck do
reduces genetic diversity by reducing the number of different alleles in the gene pool
what is a gene pool
complete range of alleles in a population
what is a population
group of organisms of one species living in a particular habitat
example of a recovery from a genetic bottleneck
nothern elephant selas went from 50 to 170,000 but has little genetic diversity than it would if htey weren’t hunted by humans
what is the founder effect
type of genetic bottleneck
what does the founder effect describe
what happens when a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool
what might occur due to the founder effect
high number of genetic disease, as an allele that was once rare would become more common (e.g in the Amish)
what does natural selection do
increases advantageous alleles in a population
what is natural selection
when individuals that contain a beneficial allele are more likely to survive and are therefore more likely to reproduce and pass the allele on, meaning the frequency of the beneficial allele increases through generations which allows species to evolve
what does natural selection lead to
better adapted populations
what are the types of adaptations
behavioural, physiological, anatomical
what are behavioural adaptations
ways an organism acts that increases its chance of survival or reproduction (e.g possums playing dead)
what are physiological adaptations
process inside an organisms body that increase its chances of survival (e.g brown bears hybernating to conserve energy)
what are anatomical adaptations
structural features of an organisms body that increase its chance of survival (e.g whale blubber)
what are the types of natural selection
stabilising selection or directional selection
what shows stabilising selection
human birth weight
what is stabilising selection
individuals with alleles for characteristics work towards the middle of the range are more likely to survive and reproduce
when does stabilising selection occur
when the environment isnt changing
what does stabilising selection reduce
the range of possible characteristics
how does human birth weight show stabilising selection
small babies = less likely to survive (hard to maintain body temp) big babies = less likely to survive (hard to give birth to) medium babies = perfect
what shows directional selection
antibiotic resistance
what is directional selection
individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce
what could directional selection survival be in response to
an environmental change
how is antibiotic resistance an example of directional selection
bacteria with resistant allele = survive and reproduce so pass onto offspring
interpreting data on the effects of selection
describe what the data shows (which type), suggest cause
testing effects of antibiotics using agar plates
liquid broth, sterile equipment, incubation at 25 degrees, inhibition zone
why are aseptic techniques used
to prevent contamination of cultures by unwanted microorganisms
what are aseptic techniques
disinfectant, flame, minimise time spent in open
what does phylogeny tell us
the evolutionary history of organisms and how closely related organisms are
what is phylogeny
the study of the evolutionary history of organisms
branches of phylogeny tree
first branch = common ancestor of all family members, now extint, close branches = closely related
what is taxonomy
science of classification, naming organisms and organising them into groups to make them easier to identify and study organisms
how many groups are there of organising organisms
8
how are these groups arranged
hierachy, largest at the top and smallest at the bottom
order of the group
domain, kingdom, phylum, class, order, family, genus, species
what is a species
a group of similar organisms able to reproduce to give fertile offspring
what is the nomenclature
naming system
what is nomenclature used for classification
binomial naming system
what is the binomial naming system
first part = genus name and has capital letter, second part = species and lower case, always written in italics or underlined if hand written
what is courtship behaviour
species specific, carried out by organisms to attract a mate of the right species
what does courtship behaviour do
prevents interbreeding and so makes mating more successful
how can courtship behaviour be useful in classification
similar courtship behaviour means more closely related
courtship behaviour examples
fireflies = pulses of light
crickets = sounds
male peacocks = colourful tails
male butterlflies = chemicals
technologies useful for clarifying evolutionary relations
genome sequencing, comparing amino acid sequence, immunological comparisons
what is genome sequencing
determining entire base sequence of an organisms DNA
using genome squencing in classification
closely related species = higher percentage of similarity in DNA base order
using comparing amino acid sequence in classification
related organisms have a similar DNA sequence and so similar amino acid sequence in their proteins
using immunological comparisons in classification
similar proteins will bind to the same antibodies, so if they bind = animals are closely related
how do we measure genetic diversity
comparing DNA base sequences (different alleles of the same gene have slightly different DNA base sequences) and comparing amino acid sequences (different alleles have different mRNA sequences so produce different proteins)
how is variation caused
genes, environment or both
what is variation
the differences that exists between individuals
how do genes cause variation
genes have different alleles that cause variation
examples of environment differences causing variation
climate, food, lifestyle
example of genes and environment causing variation
genes decides how tall an organism can grow, but nutrient availability affects how tall the organism actually grows
how to study variation
use a random sample of a population
why only use a sample
too time-consuming or impossible
why does a sample have to be random
to ensure the sample isnt biased
how to see if the variation observed is due to chance
analyse the results statistically
method to look for variation between samples
finding the mean
how do you find the mean
total of all the values in your data / number of values in the data (add all the data together and divide by how many there are)
how to find information about variation within a sample
standard deviation
what does standard variation tell you
how much the values in a single sample vary , close to mean = doesnt vary (small standard deviation) spread from mean = varies (large standard deviation)
what do error bars using standard deviation tell you
how spread out the data is (large error bar = spread out, small error bar = not spread out)
what is biodiversity
the variety of living organisms in an area
what is a habitat
the place where an organism lives
what is a community
all the populations of different species in a habitat
what does high biodiversity mean
lots of different species
what are the layers of biodiversity
local and global
what is local biodiversity
variety of different soecies living in a small habitat that’s local to you
what is global biodiversity
variety of species on earth, greater at the equator and decreases towards the poles
what is the index of diversity
method of measuring biodiversity
what is species richness
a measure of the number of different species in a community
how to work out species richness
taking a random sample and counting the number of different species
how to calculate index of diversity
N(N-1)/totaln(n-1)
N=total of all organisms
n=total in one species
which agricultural practices can reduce biodiversity (5)
woodland clearance (recudes tree habitats)
hedgerow removal (removes habitats)
pesticides (kills organisms)
herbicides (reduces plant diversity and removes habitats)
monoculture (only one type of habitat)
conservation scheme examples (3)
legal protection for endangered species, protected areas, environmental stewardship scheme that encourages farmers to conserve biodiversity
