Complexity - Lecture 11

Biological complexity

The number of parts in a biological system

unicellular complexity forms a ________ of complexity

Hiearchy

EX. Macromolecule, cell, tissue, organs and system, organism

Plants, fungi, and animals are grouped into what category?

Eukaryotes

True or false: Eukaryotes are more complex than Bacteria

True

Explain the major transitions in evolution (8)

Genetic code, Chromosomes, Cells, Eukaryotes, Sexual reproduction, multicellularity, colonies

3 Conditions Of Natural Selection

• Variation among individuals

• Heritability in variation

• Fitness (survival and/or reproduction)

True Or False: Natural selection can only happen at the individual level

False, it can happen at any level

Ex. Cellular level

Richard Dawkins argues that genes are 

ULTIMATE UNITS OF SELECTION

True or false: Fitness at a cellular level can be in conflict with fitness at the individuals level

True, Ex. Cancer

Why can genetic selection be bad?

Fitness at the cellular level can interfere with the fitness of an organism at the individual level 

EX. Cancer

True Or False: Units (cells) compete to maximize fitness

True

What solution does John Maynard Smith & Ears Szathmáry introduce for the unit level

lower level units (cells) must cooperate rather than compete to reduce the costs at the individual level

How do we help cells stay cooperative?

• prevent evolution of cells

• Make genes success by making the organism succeed 

Hoe do cells stay cooperative

• Mitosis

• Meiosis

• Development and multicellularity

What is mitosis, and what does it do

Somatic cellular division

• Regenerates tissue & organs 

meiosis

Gamete cellular division

True or false: Genomes are cloned during meiosis

False, they are cloned during MITOSIS

Do we expect evolution in mitosis (what is the exception)?

No because there is no change in allele frequency across generations since they are all identical BUT if there is a mutation during cloning than there can be evolution

How do clones prevent evolution from happening?

Cloning the genome ensures that lineages do not differ from each other therefore fitness remains the same

Meiosis

Going from diploid to haploid gametes

how does meiosis increase cooperation between cells

1. 50:50 ratio between parents

2. Independent assortment

• Both eliminate any sort of competetive advantage because they occur RANDOMLY

True Or False: Independent assortment & 50:50 ratio is a result of phenotypic plasticity

False, it’s an adaptation made to increase cellular cooperation

Mitosis Vs Meiosis 

mitosis - 

Ensures alleles don't compete with individuals

Meiosis - 

Ensures fair representation of inherited genes (50:50)

What is Meiotic Drive

One allele overrepresents during the next generation (50:50) is ruined

• reduces fitness

Over-replication 

Self replicating segments of DNA

• ensure over-representation in offspring (over 50% ratio)

transposable element

Specific gene that copies itself WITHOUT self division and imposes itself somewhere else

Where can transposable genes impose themselves?

• in another segment in the same chromosome 

• In another chromosome in the same cell

True Or False: transposable elements are uncommom

False it is VERY common, its produced A LOT of DNA of organisms on the planet 

Explain the process of Methylation 

• Methyl groups attach to the TE groups

• This acts as a flag

• Cell machinery wraps around the chromatin preventing it from performing translation

Ways that genomes stop TE

1. Methylation (silencing mechanism)

2. Transposition-selection balance

What is Transposition-selection balance? explain how it works

Individual level:

An increase in natural selection against harmful effects on the organism reduces the # of chromosomes with TEs

Gene level:

Constant production of TEs

Eventually the amount of TEs balance out 

Cooperation of cells

1. beginning at single cells rather than multicellular cell organisms

2. Separation between somatic cell and meiotic cell divisions and inheritance

3. Tumor supressors