Lecture 11

Question 1

what does the complexity of a species refer to

Answer 1

the number of parts a biological species has
- molecules –> cells –> tissue –> organ –> organism
eukaryotes > prokaryotes
greater complexity = better cooperation among previous independent units

Question 2

what is a unit of selection

Answer 2

selection acts at a specific level of biological organization ONLY IF
- there is variation among the units at that level
- they are heritable
- they have differential fitness
EX: DNA, cells, individual organisms, species, large clades

Question 3

T/F the strongest NS is on the smallest units

Answer 3

true
DNA/genes
the survival of the smallest units are the most important because all of the larger units depend on it

Question 4

explain competition on lower level units of the organization

Answer 4

lower level competition = reduced fitness at higher levels
- cancer = mutation at the cellular unit level = bad for the fitness of the organism = higher level units
IF the lower level cooperates = higher fitness

Question 5

how do the biological subunits stay so cooperative?

Answer 5

1. Mitosis and Meiosis
   - a fair representation of gene variants in
   daughter cells (evenly distributed)
   
   • ensures that alleles don’t compete with an
     individuals
2. Development and multicellularity
   
   • starting from a single cell prevents the initial competition among the cell lineages
     :. alleles will spread through a population by increasing individual fitness

Question 6

what are some ways that alleles cheat the meiosis process

Answer 6

1. meiotic drive
2. over-replication

Question 7

what is meiotic drive

Answer 7

• when an allele can bias its own transmission - spreading to a higher freq - although it is reducing individual fitness - it can rapidly eliminate alleles that actually have high fitness (unfair distribution and violation of mendels laws)

Question 8

what are transposable elements

Answer 8

over replication (TE)
“jumping genes”
inserting themselves to any location on a chromosome - but not in the correct process - causing over replication

Question 9

explain the process of over-replication using TE’s

Answer 9

TE’s = self-replicating segments of DNA and selfishly want their gene is over-represented in the offspring
- this is separate from cellular replication

Question 10

how will the TEs be silenced to not cause the expulsion of genomes

Answer 10

other alleles silence TEs and it will be favoured by NS because it affects the fitness of all the subunits of the organism
- piRNA and RNA interference may = silencing mechanisms
EX: a mutation in DDM1 gene reduced methylation (which deactivates TE) will re active them again

Question 11

what is transposition

Answer 11

a form of mutation that can disrupt a gene

Question 12

what is transposition-selection balance

Answer 12

it is a balance that works on balancing the insertion of TE’s and the selection against TE’s by NS
- NS favours against the abundance of copies from TE’s

Question 13

why is having lots of different fitness levels within an individual bad?

Answer 13

ensures that genes succeed by enhancing the fitness of the organism
- if each unit is being selected for a different type of fitness = the organism fails
- there needs to be a strong selection on the rest of the genome to maintain a higher level cohesion

Question 14

how do collections of cells stay cooperative

Answer 14

1. starting from a single cell to reduce competition
2. separate the germline with a limited number of cell divisions - prevents over-replication and mutations
3. tumor suppressors - control system for cells that are dividing and growing