3- natural selection Flashcards
natural selection
the process where individuals better adapted to their environment due to advantageous traits are more likely to survive, reproduce and pass on beneficial alleles to offspring
evolution
the change in allele frequencies in a gene pool over time, primarily due to natural selection
ways evolution happens:
- variation in phenotypes
- environmental changes and selection pressure
- advantageous alleles
- passing on of advantageous alleles
- change in allele frequency
how evolution happens- variation in phenotypes
mutations introduce a variety of phenotypes within a population, contributing to genetic diversity
how evolution happens- environmntal changes and selection pressures
changes in the environment alter the selection pressure, influencing the survival and reproduction of individuals based on their traits
how evolution happens- advantageous alleles
individuals possessing advantageous alleles have a selective advantage, enabling them to survive and reproduce more effectively
how evolution happens- passing on of advantageous alleles
these advantageous alleles are transmitted to the next generation, promoting the traits that provide a selection advantage
how evolution happens- change in allele frequency
over time, natural selection leads to a change in the frequency of alleles in a population, driving evolution
niche occupation in organisms
organisms occupy niches based on physiological, behavioural and anatomical adaptations.
niche of a species
its role within its community
species competition and survival
species sharing the same niche compete, with the better adapted species surviving. this principle forms the foundation of natural selection
types of adaptations in organisms
- physiological
- behavioural
- anatomical
physiological adaptations
biochemical processes inside an organisms body that increase chances of survival
examples of physiological adaptations
- hibernating bears lower their metabolic rate so no food is needed during winter
- extremophiles near hydrothermal vents contain heat-stable enzymes and proteins
behavioural adaptations
aspects of an organisms behaviour that aid survival
examples of behavioural adaptations
- lizards bask in the sun to warm up in the morning and burrow if it gets too hot
- bird migration
anatomical adaptions
structural features of an organism which increase chances of survival
anatomical adaptations examples
- brightly coloured petals attract pollinators
- bacterial flagella aid in movement
- blubber in certain marine mammals provide insulation
reproductive isolation
- the inability to breed successfully and produce fertile offspring due to various barriers
- helps maintain the genetic integrity by preventing or reducing gene flow
types of reproductive isolation
- biochemical isolation
- behavioural isolation
- anatomical isolation
- temporal isolation
- spatial isolation
- barriers to fertilisation
- formation of sterile hybrids
biochemical isolation
a biochemical change prevents fertilisation
behavioural isolation
a courtship dance or behaviour is not recognised or attractive to mates
anatomical isolation
differences in sexual organs can prevent successful mating
temporal isolation
different flowering or mating seasons
spatial isolation
different parts of the habitat are occupied, and they are less likely to meet
barriers to fertilisation
changes to the uterus or stigma can prevent gametes from meeting
formation of sterile hybrids
in mules, pairs of homologous chromosomes do not form in meiosis, preventing the production of viable gametes
speciation
reproductive isolation between two populations can lead to the formation of new species due to the accumulation of different genetic information over time
where does allopatric speciation occur
due to geographical isolation
allopatric speciation
1) a physical barrier (like a flood, volcanic eruption or earthquake) isolated some individuals from the main population
2) environmental conditions may vary on each side of the barrier, leading to different selection pressures
3) different characteristics will be selected for/against on different sides, changing allele frequencies due to varying advantageous traits
4) mutations occur independently in each population, altering allele and phenotype frequencies further
5) over time, the populations become unable to interbreed and are reproductively isolated, forming separate species
sympatric speciation
- occurs without geographical isolation
- factors such as temporal, behavioural or gametic isolation come into play
examples of sympatric speciation
the giant iguana lizards on the galápagos islands, with one species terrestrial and the other adapted to marine life
evolutionary race between pathogens and medicines
- an evolutionary competition exists between bacteria and the development of medicines
- this is because bacteria evolve antibiotic resistance that enable them to survive and reproduce
development of antibiotic resistance- mutations
random mutations create strains that are less susceptible or even immune to certain antibiotics. antibiotics eliminate non resistant bacteria, but resistant strains can survive
development of antibiotic resistance- survival and reproduction of resistant bacteria
the elimination of non resistant bacteria reduces competition for resources, allowing resistant bacteria to thrive. these bacteria reproduce and pass on their resistant alleles to their offspring
development of antibiotic resistance- formation of resistant populations
over time, and with continued exposure to antibiotics, a completely resistant bacterial population can form
