Biol 1620 Final

Evolution

Change in the characteristics of a population over time.

Typological Thinking

By Greek philosopher Plato

Every organism is perfect and unchanging.

Inheritance of Acquired Characters

By Jean-Baptiste de Lamarck

First to propose idea of evolution.

Parental traits are modified through use and then passed on.

Descent with Modification

Change over time produced modern, modified species from ancestral species.

Gene

Section of DNA that influences one or more hereditary traits

Genotype

Combination of alleles found in an individual

Phenotype

Individual’s observable features

Fitness

The ability of an individual to produce surviving, fertile offspring relative to that ability in other individuals in the population

Adaptation

A heritable trait that increases an individual’s fitness in a particular environment.

Darwin’s Four Postulate

Heritable variation leads to differential reproductive success.

Selection has to occur

Fossils

Traces of organisms that lived in the past.

Transitional Features

Traits in a fossil species that are intermediate between ancestral and derived species

Homology

Similarity that exists in species from common ancestor

Genetic Homology

Similarity in the DNA nucleotide sequences, RNA nucleotide sequences, or amino acid sequences

Developmental Homology

Embryos of different species

Structural Homology

Similarity in adult morphology

Acclimatization

Phenotype changes in response to changes in environment

Do not pass on

Vestigial Trait

Reduced or incompletely developed structure that has no (or reduced) function

Fitness Trade-off

Compromise between traits

Historical Constraint

Traits evolve from previous traits and constrained

Directional Selection

Change in average phenotype in one direction

Stabilizing Selection

Extremes reduce and intermediate favored

Disruptive Selection

Intermediate selected against and extremes favored.

Can cause speciation

Balancing Selection

No single allele has advantage

3 ways of Balancing Selection

1. Certain alleles favored at different times or place

2. Heterozygous have higher fitness

   1. Certain alleles favored when rare but not common

Central Dogma of Molecular Biology

DNA codes RNA which codes for proteins

Transcription

Process of using DNA to make RNA

Translation

Process of using information in mRNA to synthesize protein

Mutation

Permanent change in an organism’s DNA

Point Mutation

result from one or a small numbers of base changes

2 Ways Mutation Arise

1. Mutagens can cause changes in DNA


1. Replication error

Why mutation is important

Ultimate source of genetic variation

Germ Cells

Reproductive Cells that produce sperm or eggs

Germ-Line mutation

Mutation in egg or sperm that is passed on to next generation

Somatic Cells

Nonreproductive Cells

Somatic Mutation

Mutation is somatic cells. Does not affect offspring

Genetic Drift

Change in allele frequencies in population due to change.

Random and usually in small population

2 ways that cause genetic drift

Founders effect and bottlenecks

Founder’s effect

Group of individuals establish new population in new area.

Population Bottleneck

Sudden decrease in population size in large population

Genetic Bottlenecks

Caused by population bottleneck.

Sudden Reduction in number of alleles

Gene Flow

Movement of alleles between populations.

Reduce genetic difference between population

Horizontal Gene Transfer

Transfer of genes from one to next that are not parent and offspring.

Asexual Reproduction

Occurs through mitosis. Produces clones.

Sexual Reproduction

Occurs through meiosis and produces offspring that are genetically distinct from one another and from their parents.

During Sexual Reproduction

Reproductive cells called gametes unite to form new individual. Gametes are sperm and eggs in animals. Process is called fertilization and results in diploid cell called a zygote.

2-fold+ cost of sex

Finding a mate

Courtship

Cost of meiosis

Muller’s Ratchet

Mutation is mostly deleterious and asexual is doomed mutation meltdown and lineage goes extinct.

Only way to escape is back mutation or horizontal gene transfer.

Ways to reduce cost of sex

Sex switching

Both asexual and sexual life cycles

Increase paternal investment

Speciation

Splitting event that creates two or more distinct species from an ancestral species

Biological Species Concept

Main criterion for identifying species is reproductive isolation

Advantage Based on mechanism no error

Disadvantage Can’t work on fossils and bacteria

Prezygotic Isolation

Individuals of different species are prevented from mating successfully

5 Prezygotic Barriers

Habitat

Temporal

Behavioral

Mechanical

Gametic

Postzygotic Isolation

The hybrid offspring do not survive or reproduce

3 Postzygotic Barriers

Reduced hybrid viability

Reduced hybrid fertility

Hybrid Breakdown

Morphospecies Concept

Recognition based on similarity

Advantage observable

Disadvantage sometimes female and male look different. Too subjective

Niche

Suite of biotic and abiotic conditions a species can tolerate

Ecological Species Concept

Identify species by ecological niche

Advantage the role environment plays in controlling morphology

Disadvantage different niche can still be same species

Phylogenetic Species Concept

Identifies species based on evolutionary history

Monophyletic Group

Ancestral population and all descendants

Shared Derived Characteristics

Trait unique to a monophyletic Group

Allopatry

Population that live in different areas

Allopatric Speciation

Speciation begins with geographic isolation

2 ways geographic isolation occurs

Dispersal

Vicariance

Dispersal

A population moves to a new habitat, colonizes it, and founds a new population

Vicariance

The physical splitting of a habitat

Sympatry

Populations or species that live in same geographic area

Sympatric Speciation

Speciation among populations within same geographical area

Phylogeny

Evolutionary history of a group of organism

Paraphyletic

Includes common ancestor but not all descendants

Polyphyletic

Does not include common ancestor

Homologous Characters

Similar due to shared ancestry

Analogous Characters

Similar due to other reasons than common ancestry

Convergent Evolution

Traits when natural selection favors similar solutions to similar environmental pressures

4 Evidence to determine homologous characters

Structural

Genetic

Developmental

Phylogenetic

Coevolution

The process in which species evolve together, each responding to selective pressures from the other.

3 hypothesis for origins of life

1. Life began with spark in reducing atmosphere

2. Extraterrestrial life arrived on meteorites

3. Life began in deep sea vents with earth’s core supplying the necessary energy

RNA world concept

RNA may have carried out most of biochemical function by DNA today.

Why transition to DNA

RNA mutate frequently

DNA is more stable with proofreading function because it’s double stranded

Photoautotrophs

Uses inorganic carbon such as CO2 and sunlight

Ex. Plants

Photoheterototrophs

Uses organic carbon and sunlight

Ex. Green non-sulfur bacteria

Chemoautotrophs

Uses chemical compounds but inorganic carbon

Ex. Hydrogen bacteria

Chemoheterotrophs

Energy from chemical compounds and organic carbon source

Ex. Animals

Aerobic

Uses O2 as electron acceptor

Pigments

Key evolutionary innovation absorbs sunglight

Reaction Centers

Specific chlorophyll molecules that can capture energy from sunlight

Purple Sulfur Bacteria

Type 2 Reaction centers

Use sulfur-based photosynthesis

Green Sulfur Bacteria

Type 1 Reaction center

Cyanobacteria

Acquired green and purple bacteria reaction center types.

First organism to use water as electron donor

Hypothesis of two photosystem of Cyanobacteria

1. Horizontal Gene Transfer


1. Gene duplication and 1 gene changed

How do ability to use water impact life on Earth

Photosynthesis could occur anywhere with water and light

Oxygen release by water caused great oxidation event

How did chloroplast evolved in eukaryotic organisms

Cyanobacterium took residence in eukaryotic cell. Over time lost ability to live on its own and became chloroplast

Endosymbiosis

Process in which one cell takes up residence inside of another cell.

3 major steps in evolutionary history of photosynthesis

1. Pigments use light energy to drive movements of electron

2. Cyanobacteria incorporated 2 photosystem

   1. Photosynthesis evolved in eukaryote through endosymbiosis

Fixation

The process of turning an inorganic form into an organic form

Biological Carbon Cycle

Autotrophy and heterotrophy reverse each other from glucose and oxygen to carbon dioxide and water

Net Primary Productivity (NPP)

Photosynthesis - Autotrophic Respiration

Needed for autotrophs to grow

How do CO2 affect ocean

More CO2 causes ocean to be more acidic

Coccolithopores

Phytoplankton with carbonate shells that are microbial, eukaryotic photoautotrophs

Nitrogen Cycle

Uptake and release of N2 gas

Hydrogen or oxygen added or removed from nitrogen