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Evolutionary Processes in Plants - Coggle Diagram
Evolutionary Processes in Plants
Evolution: changes in allelic or genotypic frequencies from one generation to the next
Macroevolution: occurs between populations, involving major evolutionary trends; occurs above the species level; known as speciation
Darwin believed speciation was gradual but did not realize how old the world was
Allopatric speciation: species are geographically separated
Sympatric speciation: occurs when genetic change produces reproductive barrier between mutants and parent population
Occurs in plants in the form of polyploidy; ie having 2+ chromosome sets
Refers to the presence of 3+ chromosome sets in an organism
Reproduction: Meiosis
1n (haploid) cell replicates its genes
Tetrads form
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Growth & Repair: Mitosis:
2n (diploid) cell replicates its genes
Chromosomes align
1 more item...
Odd # chromosomes = infertile for
meiosis
Mitosis can occur with these because you need to double them anyway
Meiosis you divide twice, so it never works for odd numbers of chromosomes
Even # chromosomes = fertile
Two kinds of polyploidy:
Alloploidy: multiple sets of chromosomes from 2 or more different species; more common; sympatric speciation never occurs this way; example of hybrid speciation
Autoploidy: multiple chromosome sets from same species; this is always the vehicle for sympatric speciation
Microevolution: occurs within a population; below the species level
Natural Selection: Darwin's 4 Key Observations
Individuals vary: Even amongst a population, individuals possess differences in appearance; much of this variation is heritable
Differential reproductive success: Individuals with most suitable traits for that environment will produce more fertile offspring; leads to adaptation
Resources are limited: This leads to a "struggle for existence"
Overproduction: All species tend to produce excessive numbers
Mutations: Ultimate source of all genetic variation within species & populations
Gene Flow:
Populations exchange alleles, which means allelic frequencies change; alleles can become more or less common in chromosomal locus
We can counteract natural selection by reducing the differences in allelic frequencies between populations
Genetic Drift: Change in allelic frequencies as with last one, but this time due to
random chance
Founder Effect:
when new plants are brought in from other countries/places, remember that this is just
one plant
, and is not representative of the true genetic diversity from where they came from
Bottleneck Effect:
All known individuals are almost genetically identical; there was likely previously much more genetic diversity amongst plants until 1 or 2 species began to dominate (ie made it through the bottleneck)
Non-random mating
Inbreeding: plants mate with the plants beside them since they cannot move
Self-pollination or selfing: the individual self-fertilizes
This leads to inbreeding & more homozygotes; ie plants will mate with plants beside them
Species: a group of interbreeding natural populations that are entirely reproductively isolated from other such groups
Hybridization: when two unlike organisms (either from the same species or different species) reproduce
Phylogenetic species concept: a population must have been through evolution long enough for the adaptation or new trait to actually mean something (ie for it to be statistically significant)
Implies genetic isolation but does not require a breeding test or complete genetic isolation to determine whether two things are part of the same species
Asexual reproduction: allows a plant to clone itself quickly & efficiently
Drawback: limits genetic diversity; if a disease wipes out your plant, your entire food supply is wiped out
Apomixis: formation of seeds with embryos produced without fertilization; ie embryos are clones of the mother so not produced the old-fashioned way