Classification and Evolution Flashcards
define species
group of similar organisms capable of producing fertile and living offspring
Darwins theory of evolution is based on what observations
variation exists between members of the same species
these variations are inherited from parents
organisms tend to overproduce
populations remain stable
from darwins observations, what did he conclude
survival is a struggle
those with more advantageous characteristics survive to pass them onto their offspring
over many generations small changes can lead to changes and speciation
the modern theory of evolution is called
Neo-Darwinism
causes of variation in a phenotype
environmental and genetic factors
what are the causes of genetic variation
mutations- primary source
meiosis
random fertilisation of gametes
how do mutations cause genetic variation
changes to genes and chromosomes may or may not be passed onto next generation
causes of mutations
mutagenic agents such as ionising radiation and tobacco smoke
how does meiosis cause genetic variation
produces new combination of alleles before they are passed onto the gametes therefore they are all different
how does random fertilisation of gametes cause genertic variation
produces new combinations of allels and offspring are therefore different to parents
give examples of continuous variation
height, mass
give examples of discontinuous variation
blood type, eye colour, hair colour
what does a normal distribution curve look like
a bell shaped curve
environmental influences on genetic variation include:
climatic conditions eg temp, rainfall, sunlight
soil conditions
pH
food availability
diet is an environmental impact that can affect height
individuals genetically predetermined to be the same can height grow to different heights. This typeof variation is produced by?
polygenes and the environment
diet can affect height
continuous variation vs discontinuous variation (4)
continuous: shows a full range of intermediate values between 2 extremes determined by many genes- polygenic strong environmental influence often a normal distribution curve on a histogram discontinuous: data flows into discrete categories determined by a flow of genes weak environmental influence bar chart
define selection pressures
environmental factors that limit the population of a species
includespredation, disease, competition
effect of selection pressures
determine the frequency of alleles within the gene pool
define gene pool
total number of all the alleles of all the genes of all individuals with a population at a given time
define fitness
the ability of an organism to pass on its alleles to subsequent generations, compared with other individuals of the same species- the fittest individual produces the largest number of organisms that reproduce themselves
what are the 3 types of adaptions
anatomical, physiological and behavioural
define anatomical adaption
a mutation that has caused the physical features of an organism to change eg increased fur