Lecture 23: Evolution of Complexity

Question 1

What was Lamarck’s View on Complex Evolution?

Answer 1

All individuals had the potential to become more complex

Question 2

How can complex traits evolve by random mutation?

Answer 2

1) Traits start off simple, but can still adapt
2) Some species experience “improvements” which add greater complexity over time

Question 3

What is the “Unit of Selection”

Answer 3

Most phenotypical traits arose due to selection that increases the fitness of individuals

Question 4

When is cooperation adaptive?

Answer 4

1) High relatedness
2) Reciprocal altruism
3) Cooperation sometimes break down

Question 5

What is high relatedness?

Answer 5

Genes that lead to helping relatives can spread via natural selection

Question 6

What is reciprocal altruism

Answer 6

1) Where organisms repeatedly encounter each other
2) Mutual cooperation can lead to highest fitness

Question 7

What is an example of cooperation adaptive

Answer 7

Worker bees are sterile, but selections acts to favour non-reproductive helpers for the closely related queen

Question 8

What is cooperation?

Answer 8

Groups of organisms work or act together for common or mutual benefits

Question 9

What is the unit of inheritance?

Answer 9

Genes because the target of selection is the gene

Question 10

How do genomes stay so cooperative?

Answer 10

Many features of individual organisms prevent competition within an individual.

Question 11

How do individual genomes stay so cooperative?

Answer 11

1) Mitosis and meiosis
2) Development of multicellularity
3) Uni[arental inheritance of organelles

Question 12

How does mitosis and meiosis contribute to cooperation within genomes?

Answer 12

1) Ensuring alleles do not compete within an individual
2) Fair representation of gene variants among daughter cells

Question 13

What is multicellularity?

Answer 13

Being composed of many cells or more than one cell performing differing functions

Question 14

How does development and multicellularity contribute to cooperation?

Answer 14

Starting from a single cell prevents initial competition among cell lineages

Question 15

What is uniparental inheritance of organelles?

Answer 15

When offspring inherit their genotype from a single parent

Question 16

How does uniparental inheritance of organelles contribute to cooperation?

Answer 16

1) Chloroplasts and mitochondria replicate asexually which prevents competition within cells of different organelle genomes

Question 17

How do alleles spread through a population?

Answer 17

By increasing individual fitness

Question 18

What are two methods of cheating a fair meiosis?

Answer 18

1) Meiotic drive
2) Over-replication

Question 19

What is meiotic drive?

Answer 19

If an allele can bias its own transmission, causing an increase frequency of an allele even while reducing individual fitness

Question 20

Why is meiotic drive detrimental to fitness?

Answer 20

Meiotic drive can rapidly eliminate alleles that have higher individual fitness

Question 21

What are TE’s?

Answer 21

TE’s are transposable elements that self-replicate to ensure their own over-representation

Question 22

How do genomes not explode from transposition?

Answer 22

1) There are other alleles in the genome that silence TE’s
2) Transposition-Selection Balance

Question 23

What is Transposition-Selection Balance

Answer 23

Natural selection against harmful effects on the organism reduces abundance of chromosome copies with most TEs.

Question 24

How do spread of selfish elements occur in the Mitochondria?

Answer 24

A lack of mitosis and meiosis by plastid sets up potential for spread of selfish elements?

Question 25

How do Mitochondria stay cooperative?

Answer 25

Uniparental plastid inheritance strongly reduce competition within individuals

Question 26

How does uniparental inheritance create conflict?

Answer 26

Conflict of interests between maternal inheritance of cytoplasmic genome and biparental inheritance of nuclear genome

Question 27

What does mitochondrial mutations enhance?

Answer 27

Enhances maternal fitness even if it cost is severe to male fitness

Question 28

How do collection of cells stay cooperative?

Answer 28

1) Start from single cell
2) Separation of germline
3) Tumour suppressors or other features that regulate uncontrolled cell division