Variation Flashcards
What is variation?
Variation is the DIFFERENCES that exist between INDIVIDUALS.
What is variation within species?
Variation within species is called INTRASPECIFIC variation.
For example, INDIVIDUAL European robins weigh between 16g and 22g and show some variation in many other characteristics including length, wingspan, colour and beak size.
What is variation between species?
The variation between DIFFERENT SPECIES is called INTERSPECIFIC VARIATION.
For example, the LIGHTEST species of bird is the bee hummingbird, which weighs 1.6grams on average. The HEAVIEST species of bird is the ostrich, which can weigh up to 160kg (100 000 times as much).
What is continuous variation?
Continuous variation is when individuals in a population vary WITHIN RANGE - there are no distinct categories.
Example: HUMANS can be ANY HEIGHT within a range (139cm, 175cm, 185.9cm) NOT JUST tall or short.
Variation in Animals:
> Milk yield
E.G cows can produce any volume of milk within a range.
Variation in Animals:
> Mass
Humans can be any mass within a range.
Variation in plants:
> number of leaves
A tree can have any number leaves within a range.
Variation in plants:
> Mass
e.g. the mass of the seeds from a flower head varies within range.
Variation in microorganisms:
> Width
e.g. the width of E.Coli bacteria varies within range.
Variation in microorganisms:
> length
e.g. the length of a flagellum can vary within range.
What is discontinuous variation?
Discontinous variation is when there are two or more DISTINCT CATEGORIES - each indinidual falls into ONLY ONE of these categories, there are no intermediates.
Discontinuous variation in Animals:
> BLOOD GROUP
e.g. Humans can be group A, B, AB, or O.
Discontinuous variation in plants:
> COLOUR
e.g courgettes are either green, light green or dark green.
Discontinuous variation in plants:
> Seed shape
e.g. some pea seeds have smooth seeds and some have wrinkled seeds
Discontinuous variation in microorganisms:
> Antibiotic resistance
e.g. bacteria are either resistant or not
Discontinuous variation in microorganisms:
> Pigment production
e.g. some types of bacteria can produce a coloured pigment, some can’t.
Variation can be caused by…
Genetic factors, Environmental factors, or a combination of BOTH.
Genetic factors:
Different species have…
different genes.
Genetic factors:
> Individuals of the SAME SPECIES have the…
same genes, but DIFFERENT VERSIONS of them (called ALLELES).
Genetic factors:
> The genes and alleles in an organism makes up its…
genotype.
Genetic factors:
> The differences in GENOTYPE result in…
Variation in PHENOTYPE - the CHARACTERISTICS displayed by an organism
Genetic factors:
> Examples of variation caused ONLY by genetic factors include…
BLOOD GROUP in humans (O, A, B, or AB) and ANTIBIOTIC RESISTANCE in bacteria.
Genetic factors:
> You INHERIT your genes from your parents. This means…
Variation caused by genetic factors is INHERITED.
Environmental factors:
> Variation can also be caused by….
DIFFERENCES BY THE ENVIRONMENT,
example: climate, food, lifestyle.
Environmental factors:
> Characteristics controlled by environmental factors can…
CHANGE over an organism’s life
Environmental factors:
> Examples of variation caused ONLY by environmental factors include…
ACCENTS and whether people have PIERCED EARS.
Both:
Genetic factors determine…
the characteristics an organism is born with.
Both:
Environmental factors can…
Influence how some characteristic develop.
Both:
Height, explain why its both?
Height - genes determine how tall an organism CAN GROW (e.g. tall parents tend to have tall children).
But DIET OR NUTRIENT AVAILABILITY affects how tall an organism ACTUALLY GROWS.
Both:
Flagellum, explain why?
Genes determine if a microorganism CAN GROW a flagellum, but some will only START TO GROW in CERTAIN ENVIRONMENTS, e.g. if metal ions are present.
You can use the MEAN to look for…
Variation between samples.
To investigate variation you usually…
take samples of a population
The mean is an ….
average of the values collected in a sample.
It can be used to tell if there is VARIATION BETWEEN SAMPLES.
Most samples will include values EITHER SIDE of the MEAN…
so you end up with a bell-shaped graph - this is called NORMAL DISTRIBUTION.
A normal distribution is SYMMETRICAL about the mean.
The STANDARD DEVIATION tells you…
how much the VALUES in a SINGLE SAMPLE VARY.
It’s a measure of the SPRED of Values about the MEAN.
Sometimes you’ll see the mean written as as, e.g. 9 _+3. This means…
the mean is 9 and the STANDARD DEVIATION is 3, so most of the VALUES are spread between 6 and 12.
A large standard deviation means the…
VALUES in the sample VARY ALOT. Vice versa.
(page 124) graph
The graph shows the results of an investigation into the effects of temperature on the length of time it took for ladybird larvae to emerge as adults. Two species of ladybirdwere investigated, species A and specis B.
A) Describe the results of the study
For species A and species B, as the temperature increases the development time decreases.
The development time of species B is less affected by the temperature than species A.
(page 124) graph
The graph shows the results of an investigation into the effects of temperature on the length of time it took for ladybird larvae to emerge as adults. Two species of ladybirdwere investigated, species A and specis B.
B) Explain what causes variation within species?
Individuals within a species have different forms of the same genes (alleles), which causes genetic variation?
