Unit 2: Organisms and evolution KA: Variation and sexual reproduction Flashcards
costs of sexual reproduction (2)
-males are unable to produce offspring
-only half of the parents genome is passes onto offspring which disrupts successful parental genomes
benefits of sexual reproduction (2)
-increase in genetic variation in the population which allows for evolution and adaptation to changing environments
-allows organisms to keep running in the evolutionary arms race (RQH)
costs of asexual reproduction (2)
-low genetic variation
-cannot easily adapt to changing environments
benefits of asexual reproduction (4)
-offspring can be produced more often and in larger numbers
-one parent can produce a colony of unlimited size over time
-horizontal gene transfer and mutations increase variation
-successful genotype passes on, useful in narrow, stable niches or recolonising disturbed environments
how in terms of parasites does sexual selection increase host fitness
-hosts better able to resist and tolerate parasitism have greater fitness
-if hosts reproduce sexually, the genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites
what are the offspring in genetic cloning described as
genetically identical
define the term parthenogenesis
reproduction from a female gamete without fertilisation
under what conditions is parthenogenesis most common
-cooler climates that are disadvantageous to parasites
-regions of low parasite density/diversity
how is variation achieved in asexually reproducing populations
-mutation: during cell division
-horizontal gene transfer: plasmid transfer in bacteria and yeast
where is asexual reproduction most common
-narrow stable niches
-recolonising a disturbed environment
define the term meiosis
meiosis is the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte (germline cell)
what do homologous chromosomes have thats the same (3)
-same size
-same centromere position
-same sequence of genes at the same loci
what are linked genes
genes on the same chromosome that are near to eachother
what dies crossing over result in
new combinations of the alleles on linked genes, this increases the variation of gametes
describe meiosis I
pairing up of homologous chromosomes followed by splitting the pair of chromosomes into 2 daughter cells
describe meiosis II
sister chromatids are separated and 4 haploid gamete cells are produced
what does meiosis start with
a diploid gametocyte
