L6. Early Life

Question 1

After first life formed how did we get such diversity?

Answer 1

Biological evolution

Question 2

What is biological evolution?

Answer 2

Gradual change in the inherited traits of a population
- Change in allele frequencies in a population over time
- Driven by variation in reproductive success (fitness)

Question 3

The Darwinian Revolution

Answer 3

• Began in 1859 with the publication of “On the Origin of Species”
• He established two idea
  1. Tree of life: all species have evolved from other species
  2. Natural selection: organisms are well adapted to their environments because they accumulate traits over time

Question 4

Lamarck article on “the inheritance of acquired traits”

Answer 4

He postulates that individuals are shaped by their environments. Organs which are needed are used more and become more powerful. Those that are needed less are used less and deteriorate.

Question 5

Natural Selection

Answer 5

• individuals in a population differ in their traits
• some traits confer an advantage in a given environment
• individuals that have these traits survive and reproduce better than others
• differences are heritable so the frequency of advantageous traits will increase in the next generation

Question 6

Gene

Answer 6

a self replicating DNA unit that occupies a specific location on a chromosome and determines a particular characteristic in an organism

Question 7

Allele

Answer 7

a variant (different) form of a given gene that codes for something

Question 8

Fitness

Answer 8

reproductive success

Question 9

Phenotype

Answer 9

interaction between genotype and environment
- Phenotype refers to an individual’s observable traits, such as height, eye color and blood type.

Question 10

Plasticity

Answer 10

the ability of individual genotypes to produce different phenotypes when exposed to different environmental conditions’
- environmentally determined, non-heritable, trait differences

Question 11

Why do individuals genetics vary

Answer 11

• mutation
• mode of reproduction (ex. sexual and asexual)

Question 12

How do prokaryotes transfer information from generation to generation?

Answer 12

• binary fission (reproduction in prokaryotes)
  an enzyme gently breaks apart the two DNA strands
• other enzymes attach complementary bases to each of the old strands
• another enzyme checks for mistakes (proof-reading) and a DNA repair enzyme fixes them. Sometime mistakes get passed leading to mutations, the source of all variation.

Result: two strands virtually identical to the original

Could also occur through conjugation, transformation and transduction

Question 13

Conjugation

Answer 13

Sharing plasmids (separate ring of DNA), does not = reproduction, but introduces genetic variation

Question 14

Transformation

Answer 14

a prokaryote picks up a plasmid from the environment, does
not = reproduction, but introduces genetic variation

Question 15

Transduction

Answer 15

a virus relocates DNA from one prokaryote to another via viral
replication cycles, does not = reproduction, but introduces genetic variation

Question 16

How do eukaryotes transfer information from generation to generation?

Answer 16

• mitosis: duplicate chromosomes line up and are pulled to opposite sides of parent cell; the cell then divides (fission) to produce daughter cells
• meiosis: type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes

Question 17

Pros and Cons of Eukaryotic sexual reproduction

Answer 17

pros:
- generates a lot of variation
- DNA repair mechanism
- masking mutations, higher change that one copy works
cons:
- mate searching costs
- competition
- display costs
- breaks apart well adapted combinations at each generation

Question 18

How did eukaryote evolution arise

Answer 18

Organisms existing in around diversified prokaryotic species and in an oxygenated environment. There was high complexity, different reproductive approach and symbiosis (long-term biological interaction)

Most current hypotheses involve some sort of symbiosis and/or fusion of prokaryotes that results in the larger, more complex eukaryotic cell

Question 19

Biochemical evidence for eukaryote ancestors?

Answer 19

DNA sequence data from genes in the nucleus of eukaryotes suggest that they are more closely related to Archaea than to Bacteria

But parts of mitochondria and chloroplasts have similarities of Bacteria

Question 20

Endocytosis

Answer 20

the ingestion of large particles (such as bacteria) and the uptake of fluids or macromolecules in small vesicles.