3. Variation Flashcards
(16 cards)
What is variation
The differences that exist between individuals. Every individual organisms is unique - even clones (like identical twins) show some variation.
Where can variation occur
- Within species - called intraspecific variation. Eg. individual European robins weigh 16g-22g & show some variation in many other characteristics including length, colour, beak size.
- Between species - called interspecific variation. Eg. the lightest species of bird is the bee hummingbird (1.6g). The heaviest is ostrich (160kg).
Variation can be…
- Continuous
- Discontinuous
What is continuous variation
When the individuals in a population vary within a range - there are no distinct categories.
Eg. humans can be any weight within a range (139cm, 185.6cm, etc), not just tall or short.
see pg122 for graph eg
Continuous variation: animals example
- Milk yield - eg. cows can produce any volume of milk within a range.
- Mass - eg. humans can be any mass within a range.
Continuous variation: plants example
- No. of leaves - eg. a tree can have any no. of leaves within a range.
- Mass - eg. the mass of the seeds from a flower head varies within a range.
Continuous variation: microorganisms example
- Width - eg. the width of E.coli bacteria varies within a range.
- Length - eg. length of the flagellum can vary within a range.
What is Discontinuous variation
When there are 2 or more distinct categories - each individual falls into only one of these categories, there are no intermediates.
see pg122 for eg graph
Discontinuous variation: animals example
- Blood group - eg. humans can be group A, B, AB or O.
Discontinuous variation: plants example
- Colour - eg. courgettes are either yellow, dark green or light green.
- Seed shape - eg. some pea plants have smooth or wrinkled seeds.
Discontinuous variation: microorganisms example
- Antibiotic resistance - eg. bacteria are either resistant or not.
- Pigment production - eg. some types of bacteria can produce a coloured pigment, some cant.
What can variation be caused by
- Genes
- Environment
- Both
How do genetic factors cause variation
- Diff species have diff genes.
- Individuals of the same species have the same genes, but different alleles.
- Genes & alleles an organism has make up its genotype.
- The differences in genotype result in variation in phenotype.
- Eg’s. of variation caused ONLY by genetic factors include blood group in humans & antibiotic resistance in bacteria.
- You inherit your genes from parents, meaning variation caused by genetic factors is inherited.
How do environmental factors cause variation
- Variation can also be caused by differences in the environment eg. climate, food, lifestyle.
- Characteristics controlled by environmental factors can change over an organism’s life.
- Eg’s of variation caused ONLY by environmental factors include accents & whether ppl have pierced ears.
How do BOTH genetic & environmental factors cause variation
-
Genetic factors determine the characteristics an organism’s born with, but environmental factors influence how some characteristics develop. For eg:
- Height - genes determine how tall an organism can grow (tall parents tend to have tall children). But diet or nutrient availability affect how tall an organism actually grows.
- Flagellum - genes determine if a microorganism can grow a flagellum, but some will only start to grow them in certain environments (eg. if metal ions are present).
standard deviation (IGNORE FOR EOY MOCKS)
