Variation Flashcards
What are inherited features?
Characteristics of an organism that are determined by their genes
What are acquired features?
Characteristics of an organism that determined by their environment
Inherited features can be discontinuous/discrete or continuous. What is the difference?
Discontinuous/discrete features have a limited range of phenotype possibilities but continuous features have a wide range of phenotype possibilities
Does asexual or sexual reproduction create variation?
Sexual
Why would a species want to reproduce asexually?
It is quicker to have offspring because the parent doesn’t need find a mater
If the parent is successful within their environment, it is good for the offspring to be identical to them because they are more likely to be successful
Why would a species want to reproduce sexually?
Sexual reproduction creates genetically unique offspring. If the environment changes e.g. new disease, there is greater chance that some individuals might have the genetic makeup to survive and then reproduce
What type of cell division is involved in sexual reproduction?
Meiosis
What is the purpose of meiosis?
Type of cell division to create gametes/sex cells
Where does meiosis occur?
In sexual organs - testes in males and ovaries in females
What three processes that occur during meiosis create variation?
Segregation of alleles
Independent assortment
Crossing over/recombination
Explain how segregation of alleles creates variation
During meiosis, only one chromosome from each homologous pair is placed into each gamete. Therefore each gamete only receives one allele from each gene and therefore gametes have unique combinations of alleles which increases variation.
Explain how independent assortment creates variation
independent assortment is the random way different homologous pairs of chromosomes line up along the cell equator during meiosis. Since each gamete only contains one chromosome from each homologous pair, the gametes contain unique combinations of chromosomes and hence alleles which increases variation in the offspring..
Explain how crossing over/recombination creates variation
Crossing over is when parts of homologous chromosomes and the alleles they carry are exchanged. This creates unique allele combinations in the gametes and therefore the offspring which increases variation.
Why do each gamete e.g. sperm and an egg, are haploid - have only half the genetic information of one parent/one member from each homologous pair?
When the egg and sperm fuse during fertilisation is forms a diploid zygote - the chromosome number is restored and each chromosome exists as a homlogous pair. Because each gamete only provided half the genetic information from each parent, the offspring is genetically unique which increases variation.
What other process causes variation but doesn’t necessarily occur during meiosis?
Mutations