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
adaptations of hydrophytes
large thin leaves, stomate on upper surface
little or no waxy cuticle, water loss not a problem
long leaf stalks with large air spaces to help them float
reduced root system no need to be anchored to the ground
poorly developed xylem tissue, allows transport of water but provides little structure
xerophytes adaptations
-thick waxy cuticle layer covering upper epidermis of leaves to reduce water loss
-few stomata, or stomata that are sunken into pits surrounded by hair to reduce water loss by transpiration
-curled, rolled or folded leaves, which reduce the surface area available for transpiration
-adaptations to store water, thick succulent stem, widley spread roots to absorb as much water, very deep roots to reach undrground water syste,
describe the steps to natural selection
1- variation present in inherited characteristics shown by individual in a population
2- populations produce many offsprings more than can be supported by habitat
3-competition between individuals for resources
4-struggle for survival, indivudlas more likely to survive and reproduce
5-individuals better adapted to their enviornment are more likely to survive and reproduce
6-offsprings of better adapted individuals are more likely to inherit alleles, make them better adapted to their enviornment
7-steps repeat from one generation to the next, population changes
outline 4 steps that causes natural selection
variation
over production
selection
adaptation
describe adaptations
the process, resulting
from natural selection, by which populations
become more suited to their environment over many generations
describe antibiotic resistence
mutations may occur in the bacteria, while it reproduces very quickly, this allows them to become resistant to antibiotics
if bacteria treated with antibiotics, those that are mutated will survive while those that arent wont
the ones that survive will reproduce and pass their alleles and genes resistant to the antibiotic to their offsprings
soon whole population is resistant to the antibiotic
selective breeding
The process by which animals or plants are bred to produce offspring with particular, desirable, characteristics.
describe process of selective breeding
selection by humans of individuals with
desirable features
crossing these individuals to produce the
next generation
selection of offspring showing the desirable
features
why is selective breeding used
improve crops, and domestic animals over many generations
differences in artificial and natural selection
natural selection- driven by naturally occurring processes, variation makes most adapted organisms to survive and reproduce
artificial selection- selection imposed by humans, depends on the breeder, less variation breeder must be careful for organisms not to become so susceptible to diseases or changes in environment, has disadvantages such as inbreeding, parents may carry undesirable traits which can be passed on to offsprings
how can you make sure a plant is homozygous
produce a test cross
