2.3 variation and sexual reproduction Flashcards
(20 cards)
Name the costs and benefits of sexual reproduction.
Costs - males unable to produce offspring, only half of each parents genome passed on, disrupting successful parental genomes.
Benefits - Outweigh costs due to an increase in genetic variation. Gives raw material for adaptation giving species better chance of survival under selection pressures
The red queen hypothesis can be used to explain persistence of what?
Sexual reproduction
Parasites may select for sexually reproducing hosts why?
Hosts better able to resist parasites have greater fitness, so parasites can feed better and reprodeuce
Costs and benefits of asexual reproduction.
Costs - not able to adapt, no variation.
Benefits - whole genome passed on, one parent, unlimited colony size, larger numbers.
maintaining parent genome often an advantage in very narrow, stable niches.
Explain vegetative cloning.
Type of asexual reproduction in eukaryotes usually plants.
What is pathogenesis?
Reproduction from female gamete without fertilisation, more common in cooler climates which are disadvantages to parasites or regions of low parasite density.
What can occur to provide variation in asexually reproducing organisms?
Mutations, provide some degree of variation and enable some natural selection and evolution to occur.
Explain horizontal gene transfer.
Prokaryotes, can pass genetic information between individuals of the same generation. Which results in faster evolutionary changes as it increases variation.
What is meiosis?
Division of nucleus results in the formation of haploid gametes from a diploid gametocyte.
How is the sex of birds, mammals and some insects determined?
Sex chromosome.
What gene codes for male characteristics?
SRY gene.
Heterogametic chromosomes lack most alleles on corresponding to those on the X chromosome on their shorter Y chromosome. What is the heterogametic chromosome?
XY
What happens to the female chromosome XX?
One of the X chromosomes is randomly inactivated.
What does X chromosome inactivation prevent?
Double dose of gene products which could be harmful. Carriers less likely to be affected by deleterious mutations on one of their X chromosomes due to inactivation.
What is the species that have functioning male and female reproductive organs?
Hermaphrodites , usually need a partner to exchange gametes with.
For some species sex and sex ratio can be determined how?
Environmental factors.
What is the benefit of hermaphrodites?
In the uncommon event of encountering a partner, there is no requirement of them being a different sex to reproduce.
How is enviromental sex determined in reptiles?
Temperature of egg incubation.
Sex can change within individuals of some species due to…
Size, competition, parasitic infection.
in some species sex ratio can be adjusted due to ..
Resource availability.
