Biodiversity, Evolution, and Natural Selection Exam 1

Biodiversity

- Tree of life
- Describes the evolutionary relationships among all forms of life
- The branches represent all the lineages of organisms living today
- The leaf tips represent living taxa
- Variety of life forms; includes taxonomic, genetic, and functional diversity

Sixth Mass Extinction

Current mass extinction caused by human activities

Taxonomic Species Diversity

Total number of species in an area (species richness) or abundance-weighted measure (Shannon diversity index)

Amount of Current Named Species

1.8-2.1 million (most named species are insects)

Amount of Current Estimated Species

10 million

Genetic Diversity

Total genetic information within individuals of a population, species, or group of species and typically maintaining greater genetic diversity is better (less inbreeding, which can be bad)

Functional Diversity

Elements of biodiversity influencing ecosystem functions (species have "functional roles" in an ecosystem)

Example of Functional Diversity

If there are 16 species of bees the species diversity is 16 but the functional diversity is 1 (1 function as a pollinator)

Functional Diversity vs Functional Redundancy

- Typically higher functional diversity is good = higher productivity
- Functional redundancy can also be good = resilience (the more species that form the same function is good because they can resist extinction of pollinators)

Biodiversity Hotspot

Area where taxonomic, genetic, and functional diversity intersect (Ex. Madagascar)

What are the Benefits of Biodiversity?

Ecosystem Services

What are the 3 to 4 Ecosystem Services?

Provisioning, Regulating/Supporting, and Cultural

Provisioning Services

Provide raw materials
- Food
- Fuel
- Fiber and other materials
- Medicines
- Genetic resources

Regulating/Supporting Services

Are part of Earth's life support system and enable all other ecosystem services
- Climate moderation
- Erosion control
- Waste decomposition
- Nutrient cycling
- Pollination

Cultural Services

Enrich quality of life
- Aesthetics
- Recreation
- Education
- Spiritual value
- Human mental and physical health

Ecosystem Services

Benefits provided by ecosystems like provisioning, regulating, and cultural services

Net Primary Productivity (NPP)

Rate at which all plants in an ecosystem produce net useful chemical energy

Does high species richness and high functional diversity of species increase aspects of ecosystem function such as NPP?

- Independent variables are the variables that are changed or controlled in a study to test the effects on the dependent variable and dependent variables (or response variables) represent the outputs or outcomes whose variation is being studied
- Causation and correlation (experimental studies = causation)

Why care about biodiversity?

The average value is $33 trillion per year and the intrinsic value

Threats to Biodiversity

Factors like habitat destruction, overexploitation, and invasive species endangering species

What are the modern rates of exticintion?

100-1000 times greater than the average or "background" rate

What are the estimated loss of species per year?

5,000 to 25,000 species per year (normal rate is 1/yr)

Critically Endangered

Extremely high risk of extinction (50% chance of extinction in the next 10 years)

Endangered Species

High risk of extinction (20% chance of extinction in the next 20 years)

Vulnerable Species

Risk of extinction (10% chance of extinction in the next 100 years)

Habitat Destruction

Examples:
- Rapid deforestation of Borneo
- Atlantic coast of Brazil (forests reduced by 95%, loss of many rare/endemic species)

Habitat Degradation

- Pesticides
- Pollutants
- Noise/light
- Waste Disposal
- Water impoundment
- Fragmentation

Overexploitation

- The dominant threat for marine species (especially at the top of the food source)
- Unsustainable use of a renewable resource

Invasive Species

- Introduced to a new area, multiply rapidly and out-compete native species
- Non-native species that become established and spread in a new ecosystem

Summary of Threats to Biodiveristy

- Habitat loss is the "worst" overall
- Overexploitation is most important in marine
- Almost all species are affected by > 1 factor

Habitat Fragmentation

Division of habitats into smaller isolated fragments, impacting biodiversity

Preserving Biodiversity and the Ecosystem

Many different ways this can be done

Education Campaigns

Can help raise public awareness of conservation issues and affect public demand for unsustainable products

Ex Situ Conservation

Conservation method involving removal, breeding, and reintroduction of species to their habitat

Genetic Restoration

Efforts to counteract genetic drift and inbreeding in small populations

Wildlife Corridors

Vegetated paths reconnecting fragmented habitats for gene flow and access to resources

Seed Banks

Storage facilities preserving seeds to prevent permanent genetic diversity loss

Designing Protected Areas

National parks/forests or "no-catch" zones where fisherman cannot enter that area

Management for Invasive Species

To reduce the spread of zebra mussels ships exchange in their ballast mid-ocean

Ecosystem Restoration

Reviving degraded habitats to their original state

Management plans for Endangered Species

What are the major threats to species and what can we do so that the environment/species can be saved

Quantifying Ecosystem Services

Costa Rica pays some landowners not to deforest their land because the ecosystem services provided by the intact forest, including ecotourism, are so valuable

General Evolution

A theory that all species on Earth are related by a common ancestor and they have changed over time, and continue to change via natural selection

Evolutionary of Evolutionary Thought: What are species?

1800s: different types of unrelated organisms (existed independently)
Charles Darwin: Different types of related organisms ("descent with modification"

Evolutionary of Evolutionary Thought: Why are there differences within a species?

1800s: unimportant mistakes
Darwin: variation is vital

Evolutionary of Evolutionary Thought: Where do different species come from?

1800s: supernaturally created
Darwin: new species arise in populations that evolve by natural selection

Natural Selection

Process where organisms better adapted to their environment survive and reproduce

Allelic Frequencies

Relative frequency of an allele at a particular locus in a population

Descent with Modification

Darwin's concept that all organisms are related by common ancestry:
Species are all related to each other
Descent: All organisms are related by common ancestry
Modification: all populations of organisms change over time

Descent

All organisms related by common ancestry.

Modification

All populations of organisms change over time.

Variation

Differences within species.

What two predictions does evolution make?

Species change through time and species are related

Fossils

Provide evidence that species change through time.

Key Findings of Fossil Records

- Life on Earth is ancient
- Increasing complexity as you move up
- Most species have gone extinct (99%)
- Most that lived have changed over time
- Transitional forms

Artificial Selection

Humans "selectively" breed organisms based on desirable traits

Vestigial Trait

Structure that lost its original function over time and is now reduced in size (ex. tailbone)

Homology

Common trait inherited from a shared ancestor

Structural Homologies

Morphological (physical) traits that were inherited from a common ancestor

Genetic Homologies

Similarity in gene(s) or genome(s) between two species (Can use this to determine how closely 2 related species are; how DNA barcoding works)

Developmental Homology

Ancestral traits maintained during early development due to ancestral cues (gill pouch in the embryo of a chicken, human, and house cat)

Natural Selection Occurs When

1. Individual organisms that make up a population vary in traits (phenotypic variation)
2. Trait differences are heritable (have genetic basis coded in DNA)
3. More offspring are produced than can reproduce a. And those that reproduce most are NOT a random sample from the population (they have adaptations= species heritable traits that increase their fitness)
i. Natural selection occurs when individuals with certain heritable traits produce more offspring (=fitness) than individuals without those traits (passing on the DNA for those traits)
ii. More fit= reproduces the most

Population

Individuals of the same species living in the same area at the same time

When it comes to Natural Selection remember

Individuals NOT populations are naturally selected
Populations NOT individuals evolve

Requirements for Natural Selection to work

- Individuals that make up a population vary in traits
- Species Overproduce
- Those that survive best and reproduce most are not a random sample from the population. They have adaptations (specific heritable traits that improve fitness)

Individuals that make up a population vary in traits

How does variation arise?
i. Genetic mutations
1. The ultimate source of NEW variants (only place you can get a completely new trait)
2. Mutation: change in DNA sequence or structure (remember how these arise in traits on a central dogma level DNA->RNA->Proteins->traits)
a. Why is it important for evolution?
i. Ultimate source of new traits
b. Mutation is RANDOM
i. Mutations are like typos. They arise entirely by chance and entirely without regard to their impact on the fitness of the organism in which they occur. AKA mutation doesn't arise because an organism needs it to survive and reproduce
c. Mutations are rare
i. Even when a mutation happens it is not guaranteed to cause a trait change

ii. Genetic recombination (sexual reproduction/gene transfer)
1. Can only make up new combinations of existing mutations
a. Gene transfer (Horizontal Gene transfer)
i. Process in which a bacteria or archaea exchange genetic materials from other bacteria in the same generation (no reproduction)
b. Sexual reproduction
i. Recombine existing DNA into unique individuals by sexual reproduction. Additionally, there is resorting of existing DNA by meiosis (independent assortment and crossing over)

Those that survive best and reproduce most are not a random sample from the population. They have adaptations (specific heritable traits that improve fitness)

Ex: of adaptations
i. Camo: improves chance of survival, improves chances of reproducing, and improves chance of passing on the trait
ii. Sexy traits: increases the chances of mating= more likely to reproduce and pass your traits along 1. Dancing birds
iii. Weaponry: increase defense/offense that increases the chance of survival and reproduction

Genetic Mutations

Ultimate source of new variants, arise in traits on a central dogma level

Mutation

Change in DNA sequence or structure, important for evolution

Genetic Recombination

Recombine existing DNA into unique individuals by sexual reproduction

Species Overproduce

More offspring are produced than can reproduce

Adaptations

Specific heritable traits that increase fitness

Fitness

Ability to survive and reproduce offspring that survive to adulthood

Natural selection occurs when individuals with certain heritable traits produce more off spring (=fitness) than individuals without those traits (passing on the DNA for those traits)

Selective Pressure

External factors that affect an organism's ability to survive and reproduce.

Antibiotic Resistance in Bacteria

Selective pressure is the antibiotic and the trait that is associated with not dying in the presence of antibiotics is passed on which is why we see an increase in antibiotics

- Antibiotic resistance ALREADY existed prior to the presence of the antibiotic, the presence of the antibiotic did not CAUSE the bacteria to become antibiotic resistance

Misconception: Evolution is like a climb up a ladder

Organisms are not always getting better or more complex

Misconception: Evolution perfects organisms

Genetic constraints, trade-offs, and fitness dependence on the environment

Misconception: Selective pressures cause organisms to adapt

Selective pressures sort existing variants, they don't cause them to change

Misconception: Natural selection is a random process

Mutations leading to new characteristics are random, but individuals that survive are not

Misconception: Individuals evolve

Organisms can acclimate, but populations evolve over generations

Misconception: Natural selection = evolution

Natural selection is a mechanism within evolution, not equivalent to it

Misconception: In evolution, only the strong survive

Example: male salmons

Misconception: Some traits are too complex to evolve

Complex adaptations evolve from simple ones in a series of small steps

Evolution

Changes in allele/genotypic frequencies in a population over generations

Diploid

Organisms having 2 copies of every gene

Genes

Genetic sequences that code for proteins (traits)

Alleles

Different forms of the same gene (e.g., B- black hair, b- white hair)

Locus

The location of genes on each chromosome

Genotype

The genetic makeup of an individual at a locus or loci (e.g., BB)

Heterozygote

An individual with 2 different alleles at a particular locus (e.g., Bb)

Homozygote

An individual with 2 of the same alleles at a particular locus (e.g., bb)

Phenotype

The physical appearance of an individual (e.g., black hair)

Discrete Trait

You either have it or you don't

Complete Dominance

One allele completely masks the other, resulting in the heterozygote having the same phenotype as one of the homozygotes

Incomplete Dominance

The heterozygous condition produces an intermediate trait (e.g., red and white flower resulting in pink flowers)

Codominance

Two alleles are equally dominant, both appearing in the phenotype (e.g., white and brown cow resulting in a white cow with brown spots)

Multiple alleles

More than two alleles for a gene (e.g., blood type)

Sex-linked traits

Traits carried on the X/Y chromosomes (e.g., hemophilia)

Continuous traits

Range of differences in a trait within a population (e.g., height or skin color)