Unit 18 Flashcards
what is variation
the differences between individuals of the same species
result of continuous variation
when theres a range of phenotypes between two extremes
result of discontinuous variation
a limited number of phenotypes with no intermediates(blood groups etc)
what is discontinuous variation usually caused by
genes
what is continuous variation usually caused by
by both genes and environment
what is continuous variation
when there are small degrees of differences for a particular characteristic between individuals
what is discontinuous variation
when there are distinct differences for a characteristic with no ‘inbetweens’
what does the graph of continuous variation look like
smooth curves
what does the graph of discontinuous variation look like
blocks, step like shapes
what is phenotypic variation
when the variation is caused by genetics or environment
what is genetic variation
when the variation is completely controlled by genes
what is mutation
genetic changes
what is the result of mutation
occasionally new alleles are formed
what is gene mutation
the random change in the base sequence of DNA
what increases the chance/rate of mutation
ionising radiation(gamma and Xrays)
certain types of chemicals
what are the sources of genetic variation in populations
mutation,meiosis,random mating and random fertilization
what are adaptive features
an inherited feature that helps an organism to survive and reproduce in its environment
what is fitness
the probability of an organism surviving and reproducing in the environment in which it is found
what are hydrophytes
plants adapted to live in extremely wet conditions
what are the adaptations of hydrophytes
large air spaces in the leaves- keep them close to the surface of the water for more photosynthesis
small roots- they can extract nutrients from the surrounding water
stomata usually open all the time and found on the upper epidermis
what are xerophytes
they are plants adapted to live in extremely dry conditions
common adaptations of xerophytes
thick waxy cuticle- cuts down water loss
sunken stomata- reduces evaporation rate
small leaves-many have small needle shaped leaves
extensive shallow roots
thickened leaves or stems
what is natural selection
the individuals that have the best adaptive features are the ones most likely to survive and reproduce
why is there a ‘struggle for survival’ in many environments
many organisms produce more offspring than the environment is able to support which leads to competition for foods and other resources
what is survival of the fittest
individuals with characteristics most suited to the environment have a higher chance of survival and reproduction. These characteristics are then passed down to their offspring
leads to a greater number of individuals with the better adapted variations
what is adaptation
the process,resulting from natural selection, by which populations become more suited to their environment over many generations
how is the development of antibiotic resistant bacteria an example of natural selection
the bacteria that possess the characteristics that make it resistant to antibiotics reproduce and pass it on the next generation
what is selective breeding
to select individuals with desirable characteristics and breed them together
outline the process of selective breeding
the offspring with desirable characteristics are bred together again and again until their offspring reliably show the selected characteristics
differences between natural selection and artificial selection
artificial selection only occurs when humans intervene
in natural, the features are better adapted for survival
in artificial, the features are useful to humans
natural takes a long time to occur
artificial takes a shorter amount of time
