3.2 natural selection

Living organisms that reproduce sexually have great variation Produce excess offspring so there is constant competition for survival due to SELECTION PRESSURES (abiotic or biotic) Organisms that inherit characteristics that give them advantages are more likely to survive and pass on desired traits to offspring Organisms without this are likely to die out

changes to instinctive behaviour to be better adapted to strive. E.g. avoid hot parts of dat, burrowing, benign active when predators are inactive, social hunting behaviour, migrating

how the body works like enzymes. E.g. opening of stomata, urine concentration

structure of organism. E.g. thick blubber, large ears

Anatomical Behavioural Physiological

role of organisms within its habitat/trophic level . no two species can occupy same niche.

process by which evolution occurs. Organisms that are best adapted to specific environments are more likely to survive and reproduce and pass on advantageous alleles to offspring

different survival and reproduction of organisms with different genotypes leading to different phenotypes. These successful alleles that are best suited are passed on

sexual reproduction, random mutation, inbreeding or hybridisation

Reducing antibiotics use in humans and farm animals Better education Development of new antibiotics

Too widely prescribed People don’t complete course Lack fo basic hydrogen so s[reads antibiotic resistant organisms No financial incentive fro pharmaceutical companies to develop new antibiotics

natural selection showing change from one phenotype to another due to a change in environment.

bacteria with the resistance surve and reproduce rapidly. The more we use antibiotics the greater the selection pressure we exert on bacteria to evolve a new resistance

pressure cased by changed environment on individuals causing changes in population

NO GENE FLOW OR EXCHANGE OF ALLELES Different courtship behaviour Sperm and eggs not compatible Geographical barrier Different chromosome number

Hybridisation- 2 plant species breed and make fertile hybrids but these hybrids cannot produce fertile offspring Geographical isolation Ecological isolation - prefer different parts of habitat Seasonal isolation Behavioral isolation Mechanical isolation- genitalia

process where one species evolves rapidly to form many different species that all fill different ecological niches. After allopatric speciation

endemic species - species evolves in geographical isolation so only found in 1 space

Two populations Physically separated due to geographical barriers Different environments so different selection pressures on species, so separate gene pools and adaptations So different they can’t interbreed so 2 different species

At the start some are already resilient due to random variation. Resistance increases with increased treatment as increased selection pressure

Vary antibiotics and change selection pressure

Genetic variation Some are better adapted to survive Reproduce Pass on advantageous alleles

Disrupted

Overproduction of offspring Variation- duet to random mutations so new alleles Advantage- advantage when there is competition and state selection pressure Reproduce- pass on advantageous alleles Inherit- FREQUENCY OF ADVANTAGEOUS ALLELS IN GENE POOL INCREASE Evolve- better adapted to selection pressure Speciation