Lecture 18 sex, reproductive systems and evolution Flashcards
What are the two reproductive systems and their definitions?
Asexual(making clones of themselves, violation of Mendel laws) and sexual (separate sexes or hermaphroditic)
What are the two sexual systems and their definitions?
Dioecious (male and female organs in separate organisms) and hermaphroditism
What are the two mating systems and their definitions?
Cross-fertilization (mating with other organisms and self-fertilization (mating with yourself)
What is sexual reproduction?
When two parents contribute genetic material to offspring
What does sexual reproduction involve?(2)
Meiotic reduction division to form gametes (a division of a cell to one haploid)
Fusion of gametes (when the sperm and egg meet)
What is a asexual reproduction?
Only one parent contributes genetic material To offspring
Is meiotic reductive division required in asexual reproduction?
No
What are offspring like in asexual reproduction?
Offspring are genetic replicas of parent (look identical to parent)
What was Darwin’s view of sex?
We don’t know the cause of sexuality or why two gametes should fuse together, the whole thing is a mystery
How do Eukaryotic organism reproduce?
asexually rather than sexually
How do eukaryotes reproduce in cooler water?
Asexually
How do eukaryotes reproduce in warm water?
Sexually
What is the relationship between reproductive systems and the environment?
Different reproductive systems occur in different environments
Many perennial plants reproduce through both sexual and asexual reproduction. What are they considered because of this?
An invasive species
What are the costs of sex?(5)
Time and energy to find and attract mates (dating cost)
Risk of predation and infection (by going out to finding mate rather than reproducing with yourself)
Cost of producing males
50% less genetic transmission
Break up of adaptive gene combinations; segregation and recombination
What are the benefits of sex known as a paradox?
Why it has evolves even though it is cons
What is Two fold
cost of meiosis?
Sexual females contribute only 50% of genes to population
What is transmission biases?
when one trait is more likely to be copied than the other
What does transmission bias favour?
Asexuals in female competition
What is the relationship between asexual reproduction and alleles?
Asexuals reproduction maintains favorable combinations of alleles
What is the benefit of the AA allele combination?
AA helps adapt to wet environments
What is the benefit of the aa allele combination?
aa helps adapt to dry environment
What is the benefit of the Aa allele combination?
Aa helps adapt to neither wet or dry environments
What is a con of sexual reproduction regarding alleles?
can continuously recreate undesirable combinations of alleles
What are Hypotheses for the advantages of sex?(3)
Bringing together favourable mutations
Eliminating harmful mutations
Aids in genetic Variation
What is the tangled bank hypothesis?
sexually reproducing species have an advantage over asexual individuals in the amount of offspring they can produce in a particular environment
Which form of reproduction causes favourable variations of mutations to be brought together more rapidly?
During sex
What are Asexual Oenothera?
species are diploidand do not need chromosome segregation and recombination during meiosis
What do Asexual Oenothera have and what is the con to this?
Have more premature stop codon mutations
Leads to dysfunctional proteins
What do dysfunctional proteins in Asexual Oenothera imply?
Higher rates of protein sequence evolution
Implies greater accumulation of deleterious mutations
Why is cloning yourself the best option in a homogeneous environment?
cloning yourself may be the best strategy because lack of diversity suggest selection has built up the optimal genotype
Which type of reproduction method do heterogenous environments favour?
Sexual reproduction
What is the sex rate in homogeneous environments compared to heterogenous environments?
Sex declines rapidly in homogenous environments
Sex rate maintained at a much higher level in heterogeneous environments
What is Asexuality by parthenogenesis?
female can produce an embryo without fertilizing an egg with sperm
Which types of animals use parthenogenesis?
invertebrates
what is Asexuality by clonal propagation?
multiplication of genetically identical copies of individual plants
Which types of species go through clonal propagation?
common in plants
are many species exclusively asexual?
no
where are Asexual species usually located in phylogenies?
at the tip
how are Macroevolutionary patterns in asexual species related to extinction risk? why is this
indicates a higher extinction rate
why:
low genetic variation & accumulation of
deleterious mutations
what is the Mystery of Bdelloid rotifers?
they can go millions of years without having sex
what are mates like in terms of relativeness in outbreeding
less relative than random
what are mates like in terms of relativeness in inbreeding?
they are more related than random
what is outcrossing?
when an organism breeds with another organism that is not closely related to it
can outcrossing be inbreeding or outbreeding?
yes
what is Selfing or self-fertilization?
fusion of male and female gametes by the same individual
what is the most extreme form of inbreeding
Selfing
what causes the Fusion of gametes in outcrossing?
2 parents
what is the Fusion of gametes in inbreeding?
Fusion of gametes from 1 parent
what are Gametes derive from in outcrossing and inbreeding?
Gametes derive from meiotic reductive division
what does Local population substructure enhance?
mating among relatives
What is mating like in small populations?
even random mating can lead to mating among relatives
what do flowers do to avoid inbreeding in terms of their appearance?
develop large, showy flowers to attract pollinators
what do flowers do to avoid inbreeding in terms of their reproduction timing?
Change timing offset between male and female reproduction. specifically, pollen vs ovulation timing and when male and female flowers open
what is an example of a physiological
mechanisms to avoid selfing?
spacing of anther and stigma
what are inbreeding Avoidance Behaviors in Animals? (4)
Dispersal by one sex (one sex moving away from others of the same breed)
delayed maturation
extra pair copulation (mating with someone else other than your long-term partner)
kin recognition and avoidance (an organism’s ability to distinguish between close genetic kin and non-kin and avoid genetic kin)
how do Population genetic effects relate to genotype in inbreeding?
changes genotype frequency
how do Population genetic effects relate to homozygosity in inbreeding?
increases homozygosity
how do Population genetic effects relate to heterozygosity in inbreeding?
decreases heterozygosity
how do Population genetic effects relate to alleles in inbreeding?
no direct effect on allele frequencies
how do Population genetic effects relate to polymorphism in inbreeding?
does not affect polymorphism
what is the trends of sefling, sibling and first cousin mating on a graph describing the effect of inbreeding on the rate of heterozygosity decline depending on mating patterns?
selfing is the steepest
sibling is the second-steepest
double first cousin is the least steep
what is Inbreeding Depression?
reduced fitness of inbred offspring compared to outcrossed offspring
what are the affect of inbreeding Depression?
lower viability (survival)
lower fertility (ability to reproduce)
what does Strong inbreeding depression disfavour? what does it favour instead?
inbred offspring thus favoring outcrossed mating systems
Why can inbreeding reduce fitness?
Homozygosity of recessive deleterious alleles
The genetic consequences of inbreeding in terms of heterozygosity?
Heterozygosity (H) reduced by 50% per generation with
self-fertilization
The genetic consequences of inbreeding in terms of homozygous genotypes?
Competition between homozygous genotypes
The genetic consequences of inbreeding in terms of genetic drift?
genetic drift of small populations can reduce phenotype
what does Homozygosity for deleterious recessive alleles result in?
inbreeding depression
how many genes do out crossers produce? where do the genes come from?
2 genes in total, one from the seen and one from the pollen
how many genes do sellers produce? where do the genes come from?
three genes in total, two from the seed and one from the pollen
what condition is needed for selfing to spread and how does it spread?
If conditions are favourable selfing can spread
via natural selection
what do harmful effects of inbreeding depression encourage?
outbreeding depression
why does selfing have a lack of reproductive assurance?
due to rarity of pollinators or mates
what does “Transmission advantage from self + exported pollen” mean?
because selfers and outcrosses both transmit copies of genes through pollen but selfers transmit twice as many through seed, selfers have an automatic advantage at the gene level compared to out crossers
how does selfing do to diversity?
decreases diversity
how does selfing relate to selection?
decreases selection
how does selfing relate to extinction?
drive higher extinction rates
why is the macroevolutionary pattern of greater prevalence in outcrossing?
encourages phenotypic variability
