More Topic 4 Revsion Flashcards
Describe diploid and haploid
Diploid - has 2 complete sets of chromosomes
Haploid - has a single set of unpaired chromosomes,
Explain why the number of chromosomes is halved during meiosis
Homologous chromosomes are separated during meiosis I
explain how genetic variation within a species is increased
Random fertilisation / crossing over / independent segregation
• Creating new allele combinations / new maternal and paternal chromosome combinations
Explain the importance of meiosis
Two divisions creates haploid gametes
So diploid number is restored at fertilisation → chromosome number maintained between generations
Independent segregation and crossing over creates genetic variation
Describe how mutations in the number of chromosomes arise
Spontaneously by chromosome non-disjunction during meiosis
Homologous chromosomes (meiosis l) or sister chromatids (meiosis Il) fail to separate during meiosis
So some gametes have an extra copy (n+1) of a particular chromosome and others have
number of possible combinations of chromosomes in daughter cells following meiosis can be calculated
2^n
N is the number of homologous chromosomes
number of possible combinations of chromosomes following random fertilisation of two gametes can be calculated
(2^n)^2
N is the number of homologous chromosomes
What are alleles and how do they arise
Variations of a particular gene- different DNA base sequence
• Arise by mutation
What is a population
• A group of organisms of the same species in a particular space at a particular time
• That can (potentially) interbreed
Describe a phylogenetic classification system
• Species (attempted to be) arranged into groups, called taxa, based on their evolutionary origins (common ancestors) and relationships
• Uses a hierarchy:
Smaller groups are placed within larger groups
• No overlap between groups
What is biodiversity?
Variety of living organism
Living in a range of habitats
What is a community?
populations of different species that live in an area
Species richness
measure of the number of different species in a community
