variation and selection (topic 18) Flashcards
variation
Differences between individuals of the same species
genotypic variation
Differences between individuals of the same species due to differences in their genotypes
phenotypic variation
Differences between individuals of the same species caused by both genetic factors and environmental factors.
discontinuos variation
Differences between individuals of the same species in which there is a limited number of phenotypes with no intermediates.
cause by genes only
continuos variation
Differences between individuals of the same species in which there is a range of phenotypes between two extremes.
caused by genes and enviornment
give examples of discontinuos variation
ABO blood group
seed shapes and colour of peas
give examples of continuoes variation
body length
body mass
mutations
genetic changes
happen when there is a change in the DNA sequence of a cell
the way in which new alleles are formed
Mutations occur naturally through DNA replication errors but there are some factors that increase the rate of mutation
what are some factors that increase the rate of mutation
ionising radiation such as gamma rays, X-rays and high energy ultraviolet electromagnetic waves.
some chemicals.
gene mutation
a random change in the base sequence of DNA
what are sources of genetic variation in populations
mutation, meiosis, random mating
and random fertilisation
what is an adaptive feature
an inherited feature that helps an organism to survive and reproduce in its environment
species
A group of similar organisms that can reproduce to produce fertile offspring.
hydrophytes
An organism adapted to live in or on water.
xerophytes
An organism adapted to live in dry, arid environments