Evolution Exam 3

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Homeostasis

Ability to adjust internal environment to maintain stable equilibrium

Structural Organization

Maintain distinct parts and connections between them

Metabolism

Control of biochemical rxns

Most life shares these:

homeostasis, organization, metabolism, growth and reproduction, response to stimuli, heritability

Essential Elements

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur

Early Life and Origins

Earth formed 4.5 bya

Life building conditions 4 bya

First cells 3.5 bya

Amino Acids —>

Proteins

Nucleotides —>

Nucleic Acids

Lipids —>

Bilayer Vesicles

Miller-Urey Experiment

Simulated early earth conditions and was able to produce amino acids

Meteorites may have contributed to organic molecules

Dominant Force and First Cells

RNA likely dominant force 3.8 bya

First Cells followed shortly after 3.5 bya

Lipid Vesicles

Will spontaneously form bilayer membranes in solution (how soap works!)

Simple Vesicles can

grow by incorporating additional lipids and non-lipid molecules, as well as divide

p.s. eventually selected for over time (phospholipids)

RNA World Hypothesis

Posits that early earth had an RNA-based system in which RNA served as both the info carrier and catalyst for rxns, enzymes require RNA or nucleotide based cofactors to function, RNA is self-replicating and can be developed in labs

RNA enzymes are

Ribozymes

DNA replaced RNA because

more stable, lower mutation rate, allows larger genomes

LUCA

Last Universal Common Ancestor

not first life, a population, ancestor of all modern life

Horizontal Gene Transfer

Genes move between organisms by:

Transformation - Bacteria take up DNA from their environment

Transduction - Bacteriophages move genes from one cell to another

Conjugation - Bacteria directly transfers genes to another cell

Viral Origin Hypotheses

Escaped Genes - Selfish genetic elements that got out of the cell

Reduction Hypothesis - Parasitic cellular organisms that become extremely reduced

Relics of RNA world - remnants of the RNA world that have always existed

Major Transition Definition and examples

Fundamental reorganizations of biological structure or function leading to the potential for new pathways of evolution

Molecules —> cells

Cells —> eukaryotes

Cells —> multicellular organisms

Key component of each major transition is

Cooperation, in terms of shared reproduction, efficiency, and better info transfer

Shared reproduction means

Individuals sacrifice independent reproduction to join a larger group that shares reproduction ie your liver cells don’t have their own babies

Efficiency (economies of scale)

when a group can more effectively accomplish a task than an individual

Better info transfer refers to

information being stored and transmitted more efficiently within groupings

Multicellularity

each individual cell does not reproduce, the organism does

Clonal multicellularity (staying together)

form of multicellular life where an organism develops from a single cell through repeated divisions (mitosis), resulting in genetically identical (clonal) cells

Aggregative multicellularity (coming together)

form of multicellular life that arises when previously independent, free-living cells come together (aggregate) to form a cooperative, multicellular structure, often in response to environmental stress such as starvation

Policing Mechanisms

higher-level individual evolves ways to suppress “cheaters” and maintain the higher-order organization.

Locked-in Method

once evolved, it might be impossible or extremely difficult to go back to the pre-transition organization.

Sociality Pros vs Cons

Pros:

• Better hunting

• Predator defense

• Information sharing

Cons:

• Disease spread

• Competition

• Visibility

Eukaryotes vs Prokaryotes

3.8 bya LUCA

3 bya prokaryotic cells

1-2 bya eukaryotic cells

Endosymbiosis

a mutually beneficial relationship where one organism lives inside the body or cells of another

Example of Endosymbiosis

1. Membrane-bound organelles are

defining feature of eukaryotes.

2. Mitochondria and chloroplasts

originated as free-living bacteria.

3. Engulfed by ancestral (archaeal?)

cell and formed symbiotic

relationship.

4. Now both organelles are required for

survival by host cell

Germ Cells

Reproduction, produce gametes

Somatic Cells

specialized for maintenance and growth, and do not reproduce

Lose totipotency

Group Living

A set of conspecific individuals who affect each other’s fitness, (foraging/hunting, mating choices, predator defense benefits)

Biological Species Concept

• Same species = can interbreed

• Based on gene flow

Limitations:

• Doesn’t work for asexual species

• Hybrids complicate things

Evolutionary Species Concept

• Based on lineage over time

• Hard to test

Ecological Species Concept

• Based on niche

• Focus on resource use

Phylogenetic Species Concept

• Smallest monophyletic group

• Based on shared derived traits

Phenetic/Morphological Species Concept

• Based on physical traits

• Used for fossils

Allopatric Species

• Geographic barrier

• No gene flow

Sympatric Species

• No physical barrier

• Driven by:

  • Resource competition

  • Disruptive selection

  • Genetic changes

Parapatric Species

• Gradient (cline)

• Hybrid zone exists

Prezygotic Barries

• Habitat

• Behavioral

• Temporal

• Mechanical

Postzygotic Barriers

• Hybrid inviability

• Hybrid sterility

• Hybrid breakdown

Behavioral isolation

species-specific behaviors, such as mating rituals, songs, or pheromones, prevent interbreeding between different species

Temporal isolation

two or more closely related species (or populations) are unable to interbreed because they reproduce at different times

Habitat isolation

closely related species live in the same geographic area but occupy different habitats or niches

Mechanical isolation

Parts don’t fit

Hybrid inviability

hybrid offspring fail to develop properly, dying before or shortly after birth

Hybrid sterility

where the offspring of two different species are born healthy but are unable to reproduce

Hybrid Breakdown

where first-generation (F1) hybrid offspring are viable and fertile, but subsequent generations (F2 or backcrosses) exhibit reduced fitness, such as infertility or inviability