Chapter 5- Natural Selection Flashcards
Why does natural selection depend on variation within populations?
Because if all individuals were identical, there would be no way of some individuals being favoured more than others
There are 3 causes of variations between individuals in a species, what’s the 1st?
Mutation- new alleles are produced by gene mutation, which enlarged the gene pool of a population
There are 3 causes of variations between individuals in a species, what’s the 2nd?
Meiosis- produces new combinations of alleles by breaking up the existing combination in a diploid cell- crossing over causes genetic variation
There are 3 causes of variations between individuals in a species, what’s the 3rd?
Sexual reproduction- fusion of male and female gametes, gametes come from different parents so the offspring has a combination of alleles from two individuals
What are adaptions?
Characteristics that make an individual suited to its environment and way of life
What do species tend to do
Produce more offsprings than the environment can support
What happens when more offspring than the environment can support is produced?
Leads to a struggle for existence within a population- there will be competition for resources and not every indictable will obtain to allow them to survive - other die from predators - natural selection= fittest survives
What happens when individuals reproduce?
They pass on characteristics to their offsprings
What does natural selection increase?
The frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species
Why does natural selection increase the characteristics that make individuals better adapted ?
Because better adapted individuals survive, they can reproduce and pass on characteristics to their offspring - over generations the characteristics of the populations gradually change- natural selection 😊
Ex of natural selection - galápagos finches
14 species in total- observed all their beaks varied, as did their diet- shown that beak characters and diet are linked, when one changes so does the other - ex- 2 species medium finch and small ground finch, both feed on small seeds although medium finch can feed on larger ones - 1977 drought caused shortage of small seeds- small ground finch couldn’t eat large seeds so many died etc by 1987 the medium finches had longer narrower beaks in correlation with the lack of small seeds
explain evolution of antibiotic resistance
It is due to genes in bacteria and so it can be inherited
1) wide spread use of antibiotics
2) bacteria can reproduce very rapidly
3) populations of bacteria are often huge, increasing the chance for a gene for antibiotic resistance
4) bacteria can pass genes on to other bacterias - using plasmids etc
When can natural selection only occur?
If there is variation amongst members of the same species
