3.4.4 - Genetic diversity and adaptation Flashcards
what is genetic diversity
genetic diversity is the number of different alleles of genes in a species or population
what do alleles code for
alleles code for different versions of characteristics e.g. blonde hair or brown hair
what does a large number of different alleles in a population mean there will be
large number of different alleles in a population = large variety of different characteristics = high genetic diversity
how can it be a disadvantage if a population has a low genetic diversity
low genetic diversity = may not be able to adapt to change in environment = whole population could be wiped out by single event e.g. a disease
how is genetic diversity within a population increased (mutations)
mutations in the DNA forming new alleles. some of these can be advantageous but others can lead to problems
how is genetic diversity within a population increased (different alleles)
different alleles being introduced into a population when individuals from another population migrate into it and reproduce (gene flow)
what does genetic diversity allow to occur
genetic diversity allows natural selection to occur as some characteristics are more advantageous than others
what is a genetic bottleneck
genetic bottleneck is an event that causes a big reduction in a population
example of genetic bottleneck
when a large number of organisms within a population die before reproducing
what happens as a result of genetic bottlenecks
reduces the number of different alleles in the gene pool and so reduces genetic diversity
what happens to survivors after a genetic bottleneck
survivors reproduce and a larger population is created from a few individuals
what is the founder effect
founder effect describes what happens when just 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
founder effect: how might frequency of each allele vary in the new colony compared to original population
frequency of each allele in the new colony might be very different to the frequency of those alleles in the original population
what can founder effect occur as a result of?
founder effect can occur as a result of migration leading to geographical separation or if a new colony is separated from the original population for another reason e.g. religion
what can some mutations produce
alleles that are beneficial to an organism , helping the organism to survive in certain environments
what is natural selection
when the alleles code for a characteristic that increases the chances of an organism surviving, its frequency within the population can increase
what does natural selection result in
Natural selection results in species that are better adapted to their environment
NATURAL SELECTION
step 1
- not all individuals are as likely to reproduce as each other. there is differential reproductive success in a population
NATURAL SELECTION
step 2
- individuals with an allele that increases their chances of survival are more likely to survive, reproduce and pass on their genes (including the beneficial allele), than individuals with less advantageous alleles
NATURAL SELECTION
step 3
- this means that a greater proportion of the next generation inherits the beneficial allele
NATURAL SELECTION
step 4
- they, in turn, are more likely to survive, reproduce and ass on their genes
NATURAL SELECTION
step 5
- frequency of the beneficial allele in the population increases from generation to generation
NATURAL SELECTION
step 6
- over generations this leads to evolution as the advantageous alleles become more common in the population
what is evolution
evolution is the gradual change in species over time
what has evolution led to
it’s led to the huge diversity of living organisms on Earth
what are key factors in evolution
adaptation and selection are key factors in evolution
what are adaptations
adaptations are features that help organisms to survive in their environment
what are the 3 types of adaptations
- behavioural
- physiological
- anatomical (structural)
what are behavioural adaptations
ways an organism acts that increases its chance of survival
give an example of a behavioural adaptation
scorpions dance before mating to make sure they attract a mate of the same species, increasing likelihood of successful mating
what are physiological adaptations
processes inside an organism’s body that increases its chance of survival
give an example of a physiological adaptation
some bacteria produce antibiotics which kill other species of bacteria in the area so there is less competition so they are more likely to survive
what are anatomical (structural) adaptations
structural features of an organism’s body that increases its chance of survival
give an example of an anatomical (structural) adaptation
otters have streamlined shape so easier to glide through water so easier for them to catch prey/escape predators, increasing their chance of survival
what are types of natural selection
- directional selection
- stabilising selection
what do directional and stabilising selection both do?
affect allele frequency in different ways
what is directional selection
directional selection is where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce
what directional selection be a response to
this could be in response to an environmental change
what is stabilising selection
stabilising selection is where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
when does stabilising selection occur
it occurs when the environment isn’t changing
what does stabilising selection reduce?
it reduces the range of possible characteristics
