Unit 7 - Natural Selection

Evolution

Change of genetic makeup over time. Supported by evidence.

Natural Selection

Organisms better suited to an environment are more likely to have reproductive success. As a result those traits are more likely to be passed onto the next generation.

Competition

When organisms compete for resources. Such as food, light, space, mates, etc.

Info on Natural Selection

Some organisms have better chances of survival than others. Not all organisms in a population have an equal chance of survival. Difference in phenotypes of an organism can impact their chance of survival.

Differential Survival

The concept that individuals with heritable traits better suited to their environment are more likely to survive and reproduce than those lacking such traits

Variations

Genetic differences among a population.

Adaptations

When an organism is better suited for an environment. Which we typically see as a favorable trait. Trait typically gets passed down from generation to generation. Results in more organisms with that trait.

Why does variation happen?

Result of mutations or sexual reproduction

Fitness

Ability of an organism to survive and reproduce in an environment

Reproductive Success

As it sounds, organisms ability to reproduce

Heritability

Successfully passing on adaptations to the next generation

Biotic Environment

The living parts of an environment

Abiotic Environment

The non-living parts of an environment

Stable Environments

Tend to evolve slowly.

Unstable Environments

Tend to evolve rapidly.

Stable Environment population

Do not typically see a massive shift in population size.

Unstable Enviroment population

Do typically see a shift in population size.

Genetic Variation

Describes the genotypic and phenotypic variations of an individual in a population

Genetic Variation can lead to…

More desirable traits

Genetic Variation makes a species more likely to..

Survive an environmental change because one of the phenotypes will likely emerge as a new “best fit”

Selective Pressure

Any biotic (living) or abiotic (non-living) factor that influences survivability.

Examples of Selective Pressures:

Disease, predation, climate, and food availability

When the environment changes…

Selective Pressures also change.

A once desirable trait…

May become undesirable in a new environment

A “undesirable” phenotype may…

Decrease chance of survival

A “desirable” phenotype may…

Increase chance of survival

Variations in cells include:

-Differences in Molecular structure

-Differences in Molecular types, proteins, carbs, lipids

-Differences in the number of molecules present

Individual fitness contributes to…

Species fitness

Not every individual within a species…

Needs to show fitness for that species to continue to the next generation

Cholesterol assists in…

Regulation of membrane fluidity and cell membrane structure at high temps. As well as cell membrane fluidity at low temps.

You need a properly structured cell membrane to…

Maintain homeostasis

too much Cholesterol may reduce…

Water penetration

Animal cells dont have cell walls to counteract…

Lysis

Artificial Selection

Humans breeding certain organisms to acquire desired traits.

Artificial Selection can lead to…

More / Less genetic diversity and new phenotypes that normally wouldnt exist in nature.

Evolution is a result of…

Random occurences

Mutations are random changes in an organisms…

Genome

Mutations create…

Genetic Variation in a species

New phenotypes as a result of mutation contribute to…

Evolution via Natural Selection

Genetic Drift

Random changes in the frequency of an allele within a population

Genetic Drift is a…

Non-selective process and usually only happens in a small population

Genetic Drift can lead to…

Increased deaths rates and lower birth rates

Can lead to a decrease in population size…

Natural Catastrophes (fires, volanic eruptions, and more)

Bottleneck Events may…

Contribute to genetic drift

Bottleneck

When a large popluation suddenly dwindles down to a small population

Founder Effect

Random events that results in less genetic variation in a small population because of separation from a larger population.

Some things that can cause the Founder Effect are…

Migration and Geological events

The Founder Effect may result in…

The smaller population having different genetic makeup from the original larger population

Migration / Gene Flow

When someone decides to move to or from, a population.

Migration / Gene Flow may result in…

An increase in Genetic Variation. Or a decrease in genetic variation if too much has occured.

It is impossible for a population to evolve if…

There is no genetic variation.

Null Hypothesis

The hypothesis that states experimental variables have no relationship to each other and any observations are due to random chance

Hardy-Weinberg Equations help you determine…

Allele frequencies in a population that is non-evolving.

Hardy-Weinberg Equilibrium is achieved when…

Alleles and genotypes stay the same across generations

For a population to be in Hardy-Weinberg Equilibrium…

There must be:

1. A large population & no genetic drift

2. Absence of migration / No gene flow

3. No net mutation - No genes are modified, deleted, or duplicated

4. Random Mating - No sexual selection

5. Absence of selection - No natural selection

Hardy-Weinberg Equilibrium is…

Rarely met

Factors that can disrupt Hardy-Weinberg Equilibrium

1. Mutations - changes in nucleotide sequences

2. Organisms choosing certain mates because of certain traits. No random selection of mates essentially.

3. New genes being introduced to a population

4. Genetic Drift as a result of bottleneck or the founder effect. May change allele frequency because of environmental changes

5. Natural Selection leading to certain alleles improving or reducing fitness for individuals to survive in a given environment.

Evidence of Evolution includes:

1. Molecular

2. Morphogical (Structure)

3. Genetic Evidence

4. This list is not exhaustive*

Geographics

Characteristics of a habitat or land area

GeoLOGICAL

Features of the Earth over time

Fossils help us…

Keep track of evolution and changes in the environment

Physical Evidence of Evolution…

Looking at the phenotype of species

Biochemical Evidence of Evolution

Chemical composition of living things

Mathematical support in Evolution

Statistics and computer simulations

Morphological Homologies

Structures shared among multiple species due to common ancestry

Divergent Evolution is when…

Closely related species inhabiting distinct environments evolve different characteristics from one another

Adapative Radiation

When characteristics from a single-ancestral species rapidly diversity into various forms. Which results in the formation of many new species

Molecular Clock

Accounts for the fact that diverging species accumulate more morecular differences

Homologous Structures

Variations in a structure that was present in a common ancestor

Vestigial Structures

Reduced or obselete features that serve little or no purpose to the organism (Think tailbone on humans)

Analogous Structures

Structures that evolved independently in different species due to similar environmental conditions / selective pressures

Metabolic pathways across all domains of life are…

Conserved (think glycolysis and ATP use)

Evidence that supports common ancestry among all Eukaryotes:

1. Membrane bound organelles

2. Linear chromosomes

3. The presence of introns (non-coding) in pre-mRNA

How membrane organelles support common ancestry among all Eukaryotes

Mitochondria and Chloroplasts have double-membranes. Mitochondria and Chloroplasts have both circular chromosomes. Eukaryotes have a nuclues and a nucleolus as well as linear chromosomes. Eukaryotic organelles have similar functions (Ex: ER, Golgi, Lysosomes, Vesicles)

Linear chromosomes are…

Tightly coiled DNA with histone proteins that DNA wraps around. Chromosomes are capped with telomeres. Chromosomes have large genomes. Chromosomes are found in the nucleus

Prokaryotic genomes..

Only contain one circular chromosome and have small genomes

Genetic Changes over time lead to…

The species evolution

Cell Division:

Meiosis, Sexual Reproduction increases gamete diversity, independent asorrtment, crossing over

Environmental Disruptions

Sudden changes in the environment, changes in alleles and/or gene frequencies within a population

Strata layers arrange fossils…

In the order they were deposited

Transition fossils..

Can show evolutionary change as one group evolves into another

Pathogen

Infectious agent that can produce a disease

Pathogens can…

Evolve and cause emergent diseases

Pathogens have high…

Mutation rates. As a result, there is an increase in diversity

Pathogens are capable of…

Co-evolving with the host.

The presence of pathogens can…

Change the phenotypes selected for and against in a host population

Phylogenetic Trees and Cladograms can…

Show relationships among lineages

Phylogenetic Trees

Branched diagram showing the evolutionary relationships amongst species

Phylogenetic Trees can show…

Changes over time calibrated by fossils or a molecule clock

Cladogram

Diagram used to show evolutionary relationships amongst species

A clade includes…

Any group on a cladogram sharing a common ancestor

Traits that are lost or gained during evolution can…

Be used to construct phylogenetic trees and cladograms

Speciation

Evolutionary process where one population splits into two or mroe distinct, genetically independent species that can no longer interbreed to produce fertile offspring

Phylogenetic Trees and Cladograms can indicate…

Speciation has occured

The node is where two lines meet. Which shows…

The most recent common ancestor

The root represents…

The common ancestor of all species on the phylogenetic tree or cladogram

Molecular data typically provide…

More accurate and reliable evidence than morphological traits

Derived Character

Trait in a recent species, having evolved from an ancestral trait. Often seen a table for easier analysis.

Speciation happens…

When populations are reproductively isolated from each other

Species:

Group capable of interbreeding and exchanging genetic information to produce viable fertile offspring