Lecture 23: Evolution of Complexity Flashcards
What was Lamarck’s View on Complex Evolution?
All individuals had the potential to become more complex
How can complex traits evolve by random mutation?
1) Traits start off simple, but can still adapt
2) Some species experience “improvements” which add greater complexity over time
What is the “Unit of Selection”
Most phenotypical traits arose due to selection that increases the fitness of individuals
When is cooperation adaptive?
1) High relatedness
2) Reciprocal altruism
3) Cooperation sometimes break down
What is high relatedness?
Genes that lead to helping relatives can spread via natural selection
What is reciprocal altruism
1) Where organisms repeatedly encounter each other
2) Mutual cooperation can lead to highest fitness
What is an example of cooperation adaptive
Worker bees are sterile, but selections acts to favour non-reproductive helpers for the closely related queen
What is cooperation?
Groups of organisms work or act together for common or mutual benefits
What is the unit of inheritance?
Genes because the target of selection is the gene
How do genomes stay so cooperative?
Many features of individual organisms prevent competition within an individual.
How do individual genomes stay so cooperative?
1) Mitosis and meiosis
2) Development of multicellularity
3) Uni[arental inheritance of organelles
How does mitosis and meiosis contribute to cooperation within genomes?
1) Ensuring alleles do not compete within an individual
2) Fair representation of gene variants among daughter cells
What is multicellularity?
Being composed of many cells or more than one cell performing differing functions
How does development and multicellularity contribute to cooperation?
Starting from a single cell prevents initial competition among cell lineages
What is uniparental inheritance of organelles?
When offspring inherit their genotype from a single parent
How does uniparental inheritance of organelles contribute to cooperation?
1) Chloroplasts and mitochondria replicate asexually which prevents competition within cells of different organelle genomes
How do alleles spread through a population?
By increasing individual fitness
What are two methods of cheating a fair meiosis?
1) Meiotic drive
2) Over-replication
What is meiotic drive?
If an allele can bias its own transmission, causing an increase frequency of an allele even while reducing individual fitness
Why is meiotic drive detrimental to fitness?
Meiotic drive can rapidly eliminate alleles that have higher individual fitness
What are TE’s?
TE’s are transposable elements that self-replicate to ensure their own over-representation
How do genomes not explode from transposition?
1) There are other alleles in the genome that silence TE’s
2) Transposition-Selection Balance
What is Transposition-Selection Balance
Natural selection against harmful effects on the organism reduces abundance of chromosome copies with most TEs.
How do spread of selfish elements occur in the Mitochondria?
A lack of mitosis and meiosis by plastid sets up potential for spread of selfish elements?
How do Mitochondria stay cooperative?
Uniparental plastid inheritance strongly reduce competition within individuals
How does uniparental inheritance create conflict?
Conflict of interests between maternal inheritance of cytoplasmic genome and biparental inheritance of nuclear genome
What does mitochondrial mutations enhance?
Enhances maternal fitness even if it cost is severe to male fitness
How do collection of cells stay cooperative?
1) Start from single cell
2) Separation of germline
3) Tumour suppressors or other features that regulate uncontrolled cell division
