10.5. TYPES OF VARIATION Flashcards
1
Q
what are variations?
A
- the differences in characteristic between organisms
2
Q
what are the two types of variation?
A
- interspecific variation
- intraspecific variation
3
Q
what is interspecific variation?
A
- the widest type of variation
- between members of different species
- e.g. mouse has four legs, teeth and fur whereas a bird has two legs, two wings, a beak and feathers
4
Q
what is intraspecific variation?
A
- differences between organisms within a species
- e.g. people vary in height, build, hair colour and intelligence
5
Q
what are the two factors that cause variation?
A
- genetic material of an organism (genetic variation from inheritance)
- environment in which the organism lives (environmental variation)
6
Q
what are the genetic causes of variation?
A
- alleles
- mutations
- meiosis
- sexual reproduction
- chance/ random fertilisation
7
Q
how do alleles cause genetic variation?
A
- genes have different alleles
- with a gene for a particular characteristic, different alleles produce different effects
- individuals in a species population may inherit different alleles of a gene
8
Q
what is an example of genetic variation through alleles?
A
- gene for human blood groups has 3 different alleles (A, B and O)
- depending on the parental combination of these alleles, four different combinations can be produced (A, B, AB and O)
9
Q
how do mutations cause genetic variations?
A
- changes to the DNA sequence and therefore to genes can lead to changes in the proteins that are coded for
- these protein changes can affect physical and metabolic characteristics
- if a mutation occurs in somatic (body) cells, just the individual is affected
- however, if a mutation occurs in the gametes it may be passed on to the organisms offspring
10
Q
how does meiosis cause genetic variation?
A
- gametes are produced by this process in organisms that reproduce sexually
- each gamete receives half the genetic content of a parent cell
- before the nucleus divides and chromatids of a chromosome separate the genetic material inherited from the two parents is ‘mixed up’ by independent assortment and crossing over
- this leads to the gametes of an individual showing variation
11
Q
how does sexual reproduction cause genetic variation?
A
- the offspring produced inherits genes (alleles) from each of the parents
- each individual produced therefore differs from the parents
12
Q
how does chance/ random fertilisation cause genetic variation?
A
- many different gametes are produced from the parental genome
- during sexual reproduction it is a result of chance as to which two combine (random fertilisation)
- individuals produced therefore also differ from their siblings as each contains a unique combination of genetic material
13
Q
how does variation in organisms that reproduce asexually differ from those that reproduce sexually?
A
- asexual reproduction results in the production of clones (genetically identical)
- genetic variation can only be increased in these organisms as a result of mutation
14
Q
what are environmental causes of variation?
A
- all organisms affected, though plants affected to a greater degree due to be sessile (a lack of mobility)
- e.g. two rose bushes planted separately, one in sun will grow larger than one in shade
- e.g. presence of scars in humans, occurred as a result of accident or disease and have no genetic origin (cannot be inherited from a parent)
15
Q
what are the majority of characteristics caused by?
A
- environmental and genetic factors
- e.g. if you have tall parents, likely to inherit genes and grow to a tall height. however, if you eat a poor diet or suffer from disease you may grow to below average height
- e.g. skin colour is determined by how much melanin you have (determined at birth by genetic factors) however if you expose your skin to sunlight, more melanin is produced as protection from UV rays resulting in skin turning darker
- nature vs. nurture argument meaning it is difficult to draw conclusions about causes of a variation in a particular case
