Lecture 23 Evolution of Complexity

Question 1

what do all organisms have the inherent tendency to do?

Answer 1

become more complex

Question 1

how can complex traits evolve by random mutation?

Answer 1

traits that are selected on start off simple but are still adaptive

Question 2

what does greater complexity arise from?

Answer 2

greater cooperation among independent units. Previous independent units merge (combine to form a single entity) leading to a higher level of complexity and specialization through the division of labour (the separation of a work process into several tasks)

Question 3

What Is the ‘Unit of Selection’?

Answer 3

a biological entity such as an organells or self replicating molecule subject to natural selection

Question 4

is individual selection stronger than group selection?

Answer 4

yes because it refers to pressures that lead to individual adaptations and more selfish traits

Question 5

what traits cannot be favoured by individual selection?

Answer 5

traits that are good for the species but reduce the fitness of the individual

Question 6

when is cooperation adaptive? (3)

Answer 6

genes that lead to helping relatives can spread via natural selection

reciprocal altruism: when an organism reduces its own fitness to help another organism, occurs when organisms repeatedly encounter each other, mutual cooperation can lead to highest fitness

selection for cheaters

Question 7

how is selection on individual organisms a form of natural selection?

Answer 7

genomes are made up of unrelated genes and alleles from different places. segregation, recommendation and random mating ensure that they are passed on independently. yet genes typically persist by improving the fitness of the group

Question 7

what did Dawkins think the target for selection was and why?

Answer 7

genes because they are the unit of inheritance

Question 8

How Do Genomes Stay So Cooperative?

Answer 8

many features of individuals prevent competition within the organism by preventing evolution within individuals and aligning fitness interests. It ensures that many genes succeed by enhancing the fitness of an organism

Question 9

how do individual genomes stay so cooperative? (3)

Answer 9

1. mitosis and meiosis because it ensures alleles do not compete within an organism and that there is a fair representation of gene variants among daughter cells
2. development and multicellularity because starting from a single cell prevents initial competition between cell lineages
3. uniparental inheritance of organelles because chloroplast and mitochondria replicate asexually and prevent competition between cells within different organelle genomes

Question 10

what is positive natural selection on alleles?

Answer 10

alleles spread through a population by increasing individual fitness

Question 11

how do genomes stay cooperative in terms of fair meiosis?

Answer 11

Meiosis provides a fair representation of an allele’s fitness effects on an individuals

Question 12

what is the idea behind a “Selfish” genetic element relative to an organism’s fitness interests?

Answer 12

the phenomenon wherein unequal segregation of chromosomes or alleles during meiosis allow for the overrepresentation of that element within a population or species

Question 13

what are the effects of meiotic drive? (2)

Answer 13

increased frequency of an allele even if it reduces an individual’s fitness

can rapidly eliminate alleles that have a higher individual fitness

Question 14

what is over-replication?

Answer 14

self-replicating segments of DNA

Question 15

what is cooperation in meiosis in terms of over-replication?

Answer 15

self-replicating segments of DNA and transposable elements are separated from cellular replication to ensure their own representation in offspring

Question 16

how do genomes not explode (burst as a result of rapid production) from transposition? (4)

Answer 16

1. Starting from a single cell reduces competition among individuals
2. Separation of germline with limited numbers of cell divisions inhibits transmission of selfish cell lineages
3. Tumor suppressors and other features inhibit unregulated cell division
4. somatic mutation is inevitable in long-lived multicellular organisms

Question 17

How to Do Individual Genomes
Stay So Cooperative? (2)

Answer 17

1. Many features ensure that the natural selection within an individual is limited
2. ensure that many genes succeed by enhancing the fitness of an organism

Question 18

what is the benefit of strong selection on the rest of the genome?

Answer 18

essential to maintain a higher level cohesion (act of forming a unit whole)

Question 19

What is the con of cytoplasmic male sterility in plants?

Answer 19

Can reduce the overall fitness of the plant

Question 20

what conflicts does uniparental inheritance make?(2)

Answer 20

maternal and biparental inheritance of cytoplasmic genome

Question 21

what does it mean if a male hermaphrodite plant becomes sterile?

Answer 21

the plant is a female

Question 22

what does Cytoplasmic Male Sterility in Plants enable?

Answer 22

Leads to evolution of nuclear ‘restorer’ alleles that re-enables fertility through pollen

Question 23

what is the number fitness of an individual male plant?

Answer 23

2

Question 24

what is the number of mitochondria of an individual male plant?

Answer 24

1

Question 25

what is the number fitness of an individual male sterile plant?

Answer 25

1.2

Question 26

what is the number of mitochondria of an individual male sterile plant?

Answer 26

1.2

Question 27

what is the con of male sterility?

Answer 27

decreases fitness through pollen