Diversity, classification and variation Flashcards
What cells have the diploid number of chromosomes?
Normal body cells (two of each chromosome, one from mum and one from dad)
What cells have the haploid number of cells?
Gametes (only one copy of each chromosomes)
Describe how gametes are formed by meiosis
DNA unravels and replicates so there’s two copies of each chromosome
DNA condenses and sister chromatids join by a centromere
In meiosis one chromosomes are lined in homologous pairs, they then are separated
In meiosis two pairs of chromatids are separated by the centromere dividing
As a result four haploid cells are made
Name ways that meiosis produces genetically different cells?
Crossing over of chromatids- chromatids cross over and bits of the chromatids swap over
Independent segregation of chromosomes- It’s completely random as to which chromosome pair ends up in which daughter cell
Show how mitosis and meiosis differ
Meiosis= produces half the number of chromosomes, daughter cells are genetically different, four daughter cells Mitosis= produces same number of chromosomes, daughter cells are genetically identical, produces two daughter cells
Describe what a genetic bottleneck is
Original population, high genetic diversity A large number of the population dies Resulting in a reduced number The reduced number reproduces Leaving less genetic diversity
What is the founder effect?
Few organisms start a new colony
Frequency of each allele in new colony is different to original population
Rarer alleles may become more common and leave the colony vulnerable to disease
How does natural selection increase advantageous alleles?
Not all individuals are as likely to reproduce
Some individuals have an allele increasing their chance of survival, they reproduce and pass on genes
The greater population inherits this allele
How does natural selection allow populations to become better adapted?
Behavioural adaptions- the way an organism acts to aid survival
Physiological adaptations- processes inside the organisms body which aids survival
Anatomical adaptations- structural features increasing its survival
Name the types of selection and an example
Directional selection (antibiotic resistance) Stabilising selection (birth weight)
Talk about genome sequencing as a tool to evaluate evolutionary relationships
An entire base sequence of DNA can be determined
From this DNA between two different species can be compared in order to evaluate how closely related they are
Talk about comparing amino acids sequences as a tool to evaluate evolutionary relationships
The sequence of amino acids is determined by the base sequence of DNA
So when organisms have similar amino acid sequences it means their DNA is likely to also be similar
Talk about immunological comparisons as a tool to evaluate evolutionary relationships
Similar proteins will bind to the same antibodies
What is variation caused by?
Variation= the differences between individuals
Can be caused by genetic differences
Can be caused by environmental factors
or a combination of the two
Talk about how variations studied
A population is sampled (must be randomly, using a grid and a random number generator)
Using the mean average
