Bio 112 Basu Final Exam

Homologous Structures

Structures derived from a common ancestor, may be modified for different functions

Examples of Homologous Structures

Human, cat, whale bat arms

Vestigal Structures

Remnants of ancestral (homologous) structures with no present adaptive function

Convergence Structures

Unrelated species have similar adaptions (analogous structures) under similar environmental conditions

Convergent Evolution

Natural selection acted in a way under some conditions (torpedo shape for swimming)

Allele

One of a number of alternate forms of a DNA sequence at a particular genetic locus

What has low mutation rates?

Plants and animals

Where do mutations happen faster and why?

In prokaryotes because they have short generation times

Crossovers, independent assortment, random fertilization

Sexual reproduction can result in genetic variation by recombining alleles

Microevolution

Change in allele frequencies in a population over generations

Popultion genetics

The study of what changes the allele frequencies in populations

Three mechanisms that cause allele frequency change

1.) Natural Selection

2.) Genetic Drift

3.) Gene Flow

Morphological Species Concept Definition

Organisms that have significant morphological & anatomical differences are different species

Example of Morphological Species Concept

Sorting birds into species based on their wingspan & beak size

Biological Species Concept Definition

Organisms that are reproductively isolated from each other are different species

Members of the same biological species

-Share the same gene pool

(there gene flow between species)

-Reproductively isolated from other species (by natural biological barriers)

Prezygotic Barriers

Act before the zygote is formed

Temperal Isolation

Species have different breeding schedules

Habitat Isolation

Members of a species move or are seperated

Behavioural Isolation

Actions or behaviours impacts reproduction

Gametic Isolation

Differences in gamete cells prevent fertilization

Postzygotic Barriers

Act after hybrid zygote is formed

Hybrid Inviability

An embryo is produced, but cannot survive development

Hybrid Sterility

Different species produce a viable offspring, but they can't reproduce

Hybrid

2nd generation hybrids are feeble or sterile

1.) Directional Selection

Selects phenotypes at one end of the spectrum of existing variation Shifts the populations genetic variance toward the new, fit phenotype

2.) Diversifying Selection

-Intermediates are less fit than extremes

-Maintains diversity

-Increases genetic variance

3.) Stabilizing Variation

Intermediate types more fit than extremes, Decreases genetic variation

4.) Frequency Variation

-The fitness of a phenotype depends on how common it is in the population

5.) Sexual Selection

Success based on traits related to obtaining mates (not directly related to the environment) Leads to sexual dimorphism

Intrasexual Selection

Individuals of one sex compete directly for mates of the opposite sex

Intersexual Selection

Individuals of one sex are choosy in selecting their mates from the other sex Typically female

Genetic Variation Definition

New genes and alleles can arise by mutation or gene duplication

Genetic Variation Facts

-Mutation rates low in animals and plants relatively

-Mutations accumulate quickly in prokaryotes & viruses because they have short generation times

-Only mutations in cells that produce gametes can be passed onto offspring

Who does natural selection act on?

Natural selection acts on individuals but a population evolves

What makes evolution possible?

Genetic variation in populations make evolution possible

Phenotypic Variation

-Phenotypic variation is mostly genetic

-The environment can influence expression, creating non-heritable variation

Mechanisms of Microevolution Definition

A change in allele frequencies in a population over generation

Three Mechanisms of Microevolution

1.) Natural Selection

2.) Genetic Drift (Founder effect & bottleneck effect)

3.) Gene Flow

Natural Selection- Mechanisms of Microevolution

-Acts non-randomly on the phenotypes of individuals

-Changes allelic & genotypic frequencies of populations non-randomly

-Always leads to adaption of population to current environment

Genetic Drift

-Genetic frequency changes due to randomness

-Often occurs in small populations (like sampling errors in statistics)

Outcomes of Genetic Drift

-Random changes in allele frequency in either direction

-Often reduces genetic diversity

-One allele may become "fixed" (all other alleles lost)

The Founder Effect & Genetic Drift Definition

-A few founders start a new isolated population

The Founder Effect & Genetic Drift Facts

Founder gene pool differs from isolated source, Small population size leads to more drift, Better alleles may be lost

The Bottleneck Effect & Genetic Drift

An event drastically cuts population size

Gene Flow- Mechanisms of Microevolution

Alleles move in/out of a population

Gene flow Includes

-Migration of adults

-Dispersal of gametes, seeds & larvae

Relative Fitness Definition

Fitness is relative to other individuals in the population

Fitness Definition

Fittest= best reproductive success

Hardy Weinburg Equilibrium Definition

If a large population reproduces sexually at random, then the genetic frequencies should not change in next generation (remains in equilibrium)

Hardy Weinburg Conditions

1.) No mutations

2.) Mating is random

3.) No selection (equal survival)

4.) Very large population size

5.) No gene flow in or out

What does Hardy Weinburg let us detect?

-Microevolution

-If actual ratios ≠ expected, population is evolving

-Microevolution: an evolving population is one that is showing genetic change over generations

Phylogeny Definition

-The evolutionary history of a species & its relationship to other species

-Shown as a "tree"

Types of Phylogentic Trees

rooted, unrooted

Rooted Phylogenetic Trees

Single lineage (at base) represents common ancestor

Unrooted Phylogenetic Trees

Shows relationships but not a common ancestor

Cladistic Analysis Definition

looking at the clades and seeing similar traits

Monophyletic Group (Clade)

Consists of an ancestral species and all of its descendants

Paraphyletic Group

Consists of ancestral species and some, but not all, of its descendants

Polyphyletic Group

Includes distantly related species but does not include their most recent common ancestor

Endosymbiont Definition

A cell which lives inside another cell with mutual benefit

How Did eukaryotic Cells Evolve

-Eukaryotic cells are believed to have evolved from early prokaryotes that were engulfed by phagocytosis

-The engulfed prokaryotic cell remain undigested as it contributed new functionality to the engulfing cell (e.g photosynthesis)

-Over generations, the engulfed cell lost some of its independent utility and became a supplemental organelle

What Organelles Came Via Endosymbiosis

Mitochondria & chloroplasts are both organelles suggested to have arisen by endosymbiosis

Genome Fusion

-The eukaryotic nucleus resulted from fusing archaeal & bacterial genomes

-Gram negative bacteria, which have two membranes, resulted from fusing Archae & Gram-positive bacteria, each of which has a singular membrane

What are the two types of bacteriophage life cycles?

Lytic and lysogenic

What happens in the lytic phage life cycle?

The phage lyses the host cell after replication of their virion, releasing phage progeny to find new hosts

What happens in the lysogenic phage life cycle?

The phage genome integrates with the host genome, replicating without destroying the cell; the phages are known as temperate phages

What is a prophage?

When lysogenic phage DNA is incorporated into the host cell genome

When do lysogenic phages initiate the lytic cycle?

When conditions deteriorate for the host cell, such as a lack of nutrients

What is the first step of the lytic cycle?

Phage infects cell

What happens to the phage DNA in the lytic cycle?

Phage DNA circularizes, remains separate from host DNA

What occurs during the third step of the lytic cycle?

Phage DNA replicates & phage proteins are made, new phage particles are assembled

What is the final step of the lytic cycle?

Cell lyses, releasing phage

What is the first step of the lysogenic cycle?

Phage infects cell

What happens after phage DNA becomes incorporated into the host genome in the lysogenic cycle?

The cell divides and prophage DNA is passed to daughter cells

What triggers the excision of phage DNA from the bacterial chromosome in the lysogenic cycle?

Under stressful conditions

What occurs after the phage DNA is excised from the bacterial chromosome in the lysogenic cycle?

Phage DNA replicates & phage proteins are made, new phage particles are assembled

What is the final step of the lysogenic cycle?

The cell lyses, releases phages

When did the first organisms on Earth appear?

3.5-3.8 billion years ago

How many species of prokaryotes exist?

Millions

Where can prokaryotes be found?

Everywhere, on & in every other living organism

What role do prokaryotes play in the ecosystem?

They are essential to all life, often benign

The Ancient Atmosphere & Prokaryotes

Anoxic Definition

No molecular oxygen

Phototrophs

Autotrophic organisms that convert solar energy into chemical energy

When Did Phototrophs First Appear

Within one billion years of the formation of the earth

Cyanobacteria (Blue-Green Algae)

Evolved from simple phototrophs at least one billions years

Ancestral Cyanobacteria

-Began "oxygenation" of the atmosphere

-Increases in O2 concentrations allowed the evolution of other life forms

Prokaryotic Cell Size & Structures

-Prokaryotic cells are significantly smaller than eukaryotic cells

-Predominantly single celled organisms of the domains bacteria & archaea are prokaryotes

All Cells Have Four Common Structures

1.) The plasma membrane

2.) The cytoplasm

3.) Double stranded DNA genomes

4.) Ribosomes

The Plasma Membrane

Functions as a barrier for the cell & separates from its environment

The Cytoplasm

Complex solution of organic molecules that salts the inside of the cell

Double Stranded DNA Genome

Informational archive of the cell

Ribosomes

Sites of protein synthesis

Gram Positive Bacteria Definition

-Includes many pathogens

-Many decomposers in soil

(Ex: Bacillus anthracis (anthrax) & Clastridium tetani (tetanus))

Gram Stain Reflects Cell Wall Type (+)

-Gram + bacteria with thick PG layer

-Stains purple in gram stain

Gram Negative Bacteria

-Bacteria with thinner PG layer plus outer lipid bilayer membrane

Gram Stain Reflects Cell Wall Type (-)

-Pink in gram stain; outer lipopolysaccharide layer often toxic, resists drugs & immune system

Endotoxins

Toxic outer membranes of some gram negative bacteria,Generalized toxic effect (Salmonella; food poisoning)

What are endospores?

Endospores are dormant, non-reproductive structures produced by some bacteria under stress.