Basics of sexual reproduction structures in flowering plants
Pollen grain from anther adheres to the stigma and germinates producing a long pollen tube down the style and into the ovary. then the haploid cell fertilizes the egg cell becoming diploid
Apomixis is an asexual type of reproduction in which the plant embryos grow from egg cells without being fertilized by pollen
Whats advantageous about apomixis?
1. Lower cost, dont need to rely on attracting pollinators
2. Maintain local adaptation
3. Pass a full set of heritable info to progeny
What was Margaret Ronsheims experiment on?
wild garlic, can dilute genes if took pollen from one area with less good genes and fertlized plant. At each focal plant (home plant) she planted both home bubils and away bulbibs from many other plants. Found that home plants did better where they were born
Advantages for sexual reproduction?
1. can adapt to environmental changes, generating variability
2. reduce sibling competition-a hypothesis (parent produces 2 indentical seeds in agamospermy, when grown next to eachother, they contain same roots with interfere with one anothers growth/nutrient uptake
3. "clean seed" hypothesis- seeds are sterile, a way to escape diseases
Three forms of reproduction
1. apomictic (most uncommon)
2. sexual reproduction
3. both together (most common form)
sexual reproduction methods
1. outcrossing- pollen from one plant fertilizes another plant
2. selfing- when pollen from one plant, fertlizes itself
3. both outcrossing and selfing. 1/2 of flowering species we have tested are able to self
advantages to selfing
1. safety net- dont need other to fertilize you, got yourself
2. limited genetic variability- new traits but same genes
3. retain local adaptation
mechanisms to avoid selfing
1. time of sexual maturation of gender
2. spatial seperation of genders
3. dioecy (no selfing can occur)
(Long style example) stamen down low style up high
(Short example) style low, stamen high
Describe self incompatibility to avoid selfing?
If two plants have one allele in common, the stigma will reject pollen to avoid sexual reproduction with plants with same genes.
How does stigma reject allele if both plants have it?
1. prevent pollen grain from germination
2. can prevent or retard pollen in tube growth
3. prevent fusion
Whats gametophyte self incompatibility?
pollen in eggs are haploid in gametophyte stage so she recognizes one gene as being different but doesn't account for the second gene which may be a repeat gene she has.
Whats sporophyte self incompatibility?
Wont mate with any plant with any allele alike. The most common kind of allele that a plant obtains will be the worst mating with.
Define inbreeding depression
Detrimental affects of inbreeding such as decreased fitness resulting from the expression of harmful recessive alleles
Who is michelle dudash?
She looked at offspring to see how well the progeny do. Are the three different distances that were bred have same fitness? How fit are they? Found that the lowest fitness were the two plants that were in closer distance opposed to the plants bred at the greater distances. She backed up inbreeding depression.
What happens when you decrease size of a population?
get more inbreeding and a higher chance of inbreeding depression
Why spend more energy for further dispersal?
1. Reduce competition between siblings
2. Reduce compet. with parents
3. colonize new sites
4. avoid inbreeding
5. escape from conditions that are getting worse
6. escape disease so parent plant thats diseased will not have offspring near it
7. place seeds in specific areas that increase fitness of offspring
3. animal-ingestion, adhesion, caching (store seed for food then forget about it)
Ants and elaisomes
ants cant get through fatty seed so they store in chamber which is now hidden from seed predators once underground. seeds are already planted so in nutrient rich soil. however one disadvantage is your in a pile with your siblings (competition). Some ants rip off elaiosome and just bring back when no ant colony competition, if there is competition, take whole thing