Variation and reproduction - 2.3 Flashcards
Sexual reproduction def
Where two parents reproduce together, passing down one chromosome from each pair, to produce genetically distinct offspring.
Asexual reproduction def
Where one parent reproduces on its own, passing down both pairs of chromosomes, producing genetically identical offspring.
Advantages of sexual reproduction
Greater variation
Greater response to selection pressures
Greater resistance to parasites
Disadvantage of sexual reproduction
Only half a genome is passed on meaning successful genome is disrupted.
Only half the population will be able to produce offspring, meaning that population can grow more slowly.
Advantage of asexual reproduction
Can reproduce faster and repopulate an area much faster
Can be effective in narrow stable niches and environments
Vegetative cloning and parthenogenesis will decrease the number of individuals in a species which fail to reproduce.
Disadvantage of asexual reproduction
Lacks genetic diversity
Can decrease the chance of surviving selection pressures
Organisms which asexually reproduce will have lower resistance to parasites.
Red queen hypothesis link to sexual reproduction
Hosts which sexually reproduce will be more successful since this will increase genetic diversity of offspring, which will allow for the offspring to potentially have alleles which make them resistant to parasites, and increase the chance of survival and passing on genes further.
Vegetative cloning
Where a plant will produce a genetically identical copy of itself from a smaller part of the organism.
Parthenogenesis
Where a female will reproduce without fertilising their own gamete.
Examples of asexual reproduction in eukaryotes
Vegetative cloning and parthenogenesis
Parthenogenesis ideal conditions
Cooler climates with low parasite load and density
Method of increasing genetic diversity in asexual reproduction
Parthenogenesis allows for asexual reproduction which doesn’t produce an identical clone of the parent, this is due to a haploid gamete forming the zygote.
Example of parthenogenesis
Sharks
Example of vegetative cloning
Perennial weeds such as onions
Advantage of horizontal gene transfer
Allows for evolution occur faster since genes can be passed between organisms of the same generation.
Meiosis steps in order
Interphase 1
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1 and cytokinesis
Prophase 2
Metaphase 2
Anaphase w
Telophase
Somatic cells definition
Cells that she not gametes
Gamete definition
Haploid cells which fuse together to form a zygote.
Mitosis steps
Prophase
Metaphase
Anaphase
Telophase
Interphase.
Mitosis definition
Where somatic cells divide to form more somatic cells.
Interphase
The chromosomes duplicate to form sister chromatids attached at the centromere
Centromere definition
The section where two sister chromatids are pulled apart by spindle fibres.