Lecture 6 Flashcards
Parthenogenesis
Asexual reproduction
- embryo develops from the egg w/o fertilization of sperm
Clonal propagation
Asexual reproduction
- offspring is created from a piece of the mother
- budding in plants
- cutting a stem and re planting it
- makes identical clones
What are the 2 types of sexual systems
- Dioecious
- Hermaphrodite
Explain dioecious
type of sexual system
either male or female and they only produce 1 type of gametes
male = sperm
female = egg
Explain hermaphrodite
type of sexual system
produces both male and female gametes
- common in plants
- can either self-fertilize or cross fertilize
Sexual reproduction
2 parents
meiosis
fusion of gametes
Cross fertilization
combines gametes with another plant
- flowering plant = egg
- bees = pollen to fertilize
- not clones
Self-fertilization
produces ovule and pollen
- reproducing with themselves
- offspring is not a clone (undergo meiosis, independent assortment)
asexual reproduction
1 parent
no meiosis
clones
T/F
some species have the ability to reproduce SS or AS
True
Water fleas
depending on the environment
What are the costs to sex
- Two-Fold Cost
- a female only contributes 50% of its genes to the next generation
- giving away opportunity for the offspring to increase fitness - can continuously re-create unfavorable combinations of alleles
- time and energy to find mates
- risk of predation and infection while seeking mates or mating
- costs of producing males - if AS successful then why do we need males
What are the benefits of sex
- Favorable combinations of mutations brought together more rapidly by sex
- the fit combination spreads quicker - Bringing together favorable mutations and eliminations of harmful mutations
- when crossing 2 heteros, it gives 4 different combinations - some can get rid of the mutations - Hypotheses for the advantages of sex
- lottery models (some combinations can be fit for the environment)
- what’s fit in one generation may not be fit for another gen
T/F
it is harder to get rid of bad mutations in sexual reproductive organisms
FALSE
in AS organisms, it is harder to get rid of because they keep cloning
T/F
the long term consequence of AS reproduction is too much mutations = extinction
true
Outbreeding
mates less closely related than random
- random species mating
Inbreeding
mates are relatives and are not random species
- sometimes species have no choice by to mate with relatives
Selfing and asexual reproduction are the same thing
self-fertilization and AS reproduction are not the same
- AS = clones
- Selfing = meiosis
How do species prevent inbreeding
plants: timing of male and females are different
- self-incompatibility
- parents stop reproducing after offspring
- makes disperse after mating
- increases homozygosity
- decreases heterozygosity
Inbreeding depression
the reduction in fitness of inbred offspring compared to the offspring that are outcrossed
- lower survival
- lower fertility
- strong inbreeding depression = unfavour
T/F
Inbreeding depression can change allele frequencies
TRUE
- increase homozygosity and less heterozygosity
Selfing
if conditions are favourable selfing can spread via NS
- less dependent on pollinators or mates
LONG TERM: leads to low diversity and inefficient selection
- can drive higher extinction rates
