UCD BIS 2B - Final Review (Last 1/3 of class 25-35)

Intraspecific positive interactions

Individuals may benefit from higher densities of conspecifics due to increased probability of finding mates, reduced risk of predation (schooling, masting), cooperative foraging or breeding

What is an example of an intraspecific positive interaction?

Lamb survival of bighorn sheep increases with population density due to reduced individual predation risk

What is broadcast spawning?

Releasing eggs and sperm into the water to be fertilized externally

What increases fertilization success with broadcast spawning?

An increase in density increases fertilization success through broadcast spawning.

What is mutualism? (+,+)

an interaction where both organisms benefit

What is commensalism? (+,0)

An interaction where one organism benefits and the other is unaffected

What is facilitation? (+,0)

An interaction where one organism benefits and the other is unaffected

What is the collective term for mutualism, facilitation, and commensalism?

Positive interactions: interactions among two organisms that benefit at least one organism and do not harm eachother

NOT ALTRUISM

Why should mutualism not be confused with symbiosis?

Symbiosis (living close together) can be beneficial or parasitic; mutualism can only be beneficial

What is an obligate mutualistic relationship between organisms?

At least one species could not grow and reproduce without the other

What is a facultative mutualistic relationship between organisms?

Both organisms may do better with their partner species, but can survive and reproduce without it

What are the modes of speciation?

Allopatric & Sympatric speciation (geographic isolation and speciation w/o geographic isolation

What is the morphological species concept?

The difference between species is based on morphological similarity

What is the biological species concept?

Groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups

2 individuals are members of the same species if they can mate and produce viable, fertile offspring in the wild

Reproductive isolation allows populations to evolve independently and is critical for speciation to occur

What is the lineage species concept

A group of organisms descended from a common ancestor

What is speciation?

The origin of two species from a common ancestral species with the evolution of biological barriers to gene flow - one lineage splits into two

What is a node?

Point when one lineage splits into two sister species

What do phylogenies do?

They tell the history of speciation events

What is allopatric speciation?

New species arise from geographically isolated populations: geographic barrier prevents gene flow & genetic incompatibilities

What is sympatric speciation?

New species arise in the same geographic region

The problem: how to prevent gene flow between sympatric incipient species?

What causes new species to evolve on islands?

Founder effects & natural selection

What is ecological speciation? (controversial)

Host or habitat specialization, disruptive selection, assortative mating

What is polyploidy?

Genetic mechanism for abrupt and reproductive isolation and speciation (can occur through genome duplication)

What is autopolyploidy?

Duplication of one species' genome

What is allopolyploidy?

Hybridization of two species followed by genome duplication

How do genetic incompatibilities arise during speciation?

Abrupt reproductive isolation of polyploid from diploid ancestors

Gradual accumulation of genetic incompatibilities in allopatric populations

- Chromosomal rearrangements

-Dobzhansky-Muller incompatibility (epistatic mutations)

What is Dobzhansky-Muller incompatibility?

Breakup of "coadapted gene complexes"

model of the evolution of genetic incompatibility, important in understanding the evolution of reproductive isolation during speciation and the role of natural selection in bringing it about.

The model states that genetic incompatibility is most likely evolved by alternative fixation of two or more loci instead of just one, so that when hybridization occurs, it is the first time for some of the alleles to co-occur in the same individual. For example, imagine two populations that only recently separated geographically. Both sides are starting with the same genotype AABB. One population can then evolve to aaBB, through the transition state AaBB, while the other evolves to AAbb, through the transition state AABb. During these processes, a allele will co-occur with A and B alleles, and b will co-occur with A and B alleles, without fitness consequences. When hybridization occurs, it is the first time a and b alleles co-occur, and they are the alleles that are incompatible

Example of D-M incompatibility

In Arabidopsis Thaliana -

Incompatible epistatic combinations of alleles of two genes involved in disease resistance cause a deleterious hyperimmune response in hybrids between two populations

What is post-zygotic reproductive isolation?

Hybrid incompatibilities cause reproductive isolation between diverging species

What are the three types of Post-Zygotic isolation

1. Hybrid Inviability - Mating occurs, zygotes are formed, but because of genetic incompatibilities during development, but the zygote DOES NOT DEVELOP

2. Hybrid Sterility - Hybrid zygotes develop into adults, but the adults usually do not form viable gametes, so genes cannot move from one species into another

3. Hybrid Breakdown - FERTILE hybrids form between two species, but these hybrids have low reproductive success, or their F2 offspring are sterile

What are the two types of reproductive isolation mechanisms?

Postzygotic and prezygotic

What are the types of prezygotic isolation?

Geographic, ecological, temporal, behavioral, mechanical, gametic incompatibility

What is geographic isolation?

Allopatric species have little opportunity for mating or gene flow due to geographic difference

Species with low dispersal ability can be isolated by short geographic distances

What is ecological isolation?

If two sympatric species use different habitats, they will rarely encounter one another

Even if they were reproductively compatible, they never actually mate, so they are reproductively isolated

EG microhabitat specialists in three-spine sticklebacks

In the lab, the types can mate and produce fertile offspring, but in nature, they're reproductively isolated. These are considered "incipient species"

What is temporal isolation?

Species that breed at different times of day, at different seasons, or in different years, cannot mate

Temporal Isolation

-Evidence from comparing allopatric and sympatric populations:

How will natural selection act on breeding time to reinforce reproductive isolation in sympatric populations?

Selection for lower hybridization reinforces temporal reproductive isolation in maize

What is behavioral isolation?

Many organisms recognize members of their own species courtship behaviors, songs, chemical signals, or visual cues

Eg. male fireflies attract females of their own species with a species-specific set of flashes and flying patterns

Eg birds of paradise courtship dances

Is there evidence for reinforcement of behavioral isolation?

-Pollinator-mediated behavioral isolation

How do alternate pigment alleles affect pollinator visitation?

What is mechanical isolation?

If u aint the right species it just won't fit

Mechanical isolation in Gongora orchids by physical partitioning of euglossine bee surface

What is gametic incompatibility in reproductive isolation?

Even if mating is successful, gametes are incompatible and do not fuse to form a zygote

What is Incipient Speciation?

When two groups are beginning to diverge, but there is not yet reproductive isolation. First step of speciation

What is Evolutionary Radiation?

Rapid proliferation of many species from a single ancestor. An evolutionary radiation is an increase in taxonomic diversity or morphological disparity, due to adaptive change or the opening of ecospace.

What causes evolutionary radiation?

Key innovations (increase speciation rate), ecological specialization, sexual selection, and vacant ecological niches

What is a Key Innovation?

An adaptation which enhances the diversification rate of a lineage

What is a community?

A group of species that coexist and interact within a defined area

What is ecological succession?

When a community assembles in a newly created habitat or reassemble following a DISTURBANCE

What is succession?

The pattern of changing species composition as a result of colonization and species interactions in a new habitat or after a disturbance

What are the stages of succession?

1. Disturbance

2. Early succession - pioneer species

3. Mid successional

4. Late successional - K-selected species

What are the three types of succession?

Primary, Secondary, and Cyclical succession

What is primary succession?

A habitat that does not have any living organisms or legacy of organisms.

What is secondary succession?

A habitat that has been disturbed, but contains a legacy of organisms that lived there before.

What is cyclical succession?

A pattern of change in community composition (succession) due to recurring events or changing interactions between plants and animals.

When is Sebastian Schreiber's Birthday?

May 18th, 1967

What can cause primary succession?

A new habitat or a large disturbance

What are the 2 modes of succession?

Facilitative and inhibition

What is facilitation in succession?

Specific pioneer species are necessary to modify environment before later species can colonize

What is inhibition in succession?

Early colonists make environment less suitable for subsequent colonization

What do lines in the food web indicate?

Who is eaten by whom

What defines the "who and whom" in a food web?

They can be defined as a species or a collection of species

On average, how many links separate species pairs in a food web (within a community?)

2

cool quote

"I read somewhere that everybody on this planet is separated by only six other people. Six degrees of separation between us and everyone else on this planet. The President of the United States, a gondolier in Venice, just fill in the names. I find it A) extremely comforting that we're so close, and B) like Chinese water torture that we're so close because you have to find the right six people to make the right connection... I am bound to everyone on this planet by a trail of six people." -John Guare

How do we analyze food webs with all interaction types?

Direct effects of species interactions

What is an indirect effect in a food web?

A change in the abundance of one species resulting from its interaction with another species which is affected by a third species

How do we denote an indirect effect in a food web?

A dotted line

What is a keystone species?

Species that have a major effect on community structure, and an effect disproportionate to their abundance

What is a foundation species?

Species that have a major effect on community structure by virtue of their high biomass and habitat-forming characteristics

What is Apparent Competition?

For species sharing a common predator, increasing the density of one species decreases the density of the other: the species 'appear to be competing'

(decrease one increases the other)

How can orcas affect kelp forests?

In some communities, orcas have begun to feast on sea otters: causing an increase in urchin population (prey for otters), and a decrease in kelp forests due to the increase in urchins. This creates urchin barrens where kelp forests used to be.

What effect does niche partitioning have?

It leads to increasing diversity when habitat (or resource) diversity is high

What is niche partitioning?

The process by which natural selection drives competing species into different patterns of resource use or different niches. Coexistence is obtained through the differentiation of their realized ecological niches.

What is the Intermediate Disturbance Hypothesis?

When disturbance is low, only k-selected species exist, when it is high, only r-selected species exist, when it is intermediate, both r and k species can coexist and therefore diversity is highest with intermediate levels of disturbance.

What is the Intermediate Predation Hypothesis?

Essentially diversity is maximized at intermediate levels of predation. Many species can coexist at high diversity if predation is intermediate.

(low predation means only competitively dominant species can exist, at high predation only well-defended species can exist).

What is the Intermediate Productivity Hypothesis? (productivity ~ nutrient availability)

Diversity is maximized at intermediate levels of productivity. At low levels of productivity, only few species can survive; at high levels, only competitively dominant species exist; at intermediate productivity, both of those types can coexist.

What does it mean to be Competitively Transitive?

Whenever species A excludes species B and species B excludes species C, it follows that A excludes C.

If a group of species are not competitively transitive, what are they?

Competitively Intransitive (like rock, paper, scissors)

How can so many species of algae share the same resources, yet coexist?

HYPOTHESIS: Temporal fluctuations in environmental conditions

What are Temporal Fluctuations?

Variations that change with time. (In algae populations, change in productivity)

After enough time, what happens to productivity?

Productivity increases with species richness

How does diversity influence invasion resistance?

Adding species will increase the competition coefficient between species, decreasing the likelihood of coexistence with invading species: the higher the diversity, the higher the protection against invasion.

As you add species, the probability of establishment of new species should decrease

What is an ecosystem?

All of the organisms in an ecological community as the physical and chemical factors that influence those organisms.

Are ecosystems all the same size?

No - ecosystems vary in size. Like communities, small ecosystems are "stacked" within larger ones, and the boundaries are sometimes unclear.

What services do ecosystems provide?

Provisioning services, Regulating services, Cultural services

What are Ecosystem Services?

The capacity of ecosystems to provide goods and services that satisfy human needs, either directly or indirectly.

What are Provisioning Services?

Any type of benefit to people that can be extracted from nature (eg. food, clothing, water, timber, fuel, and medicine)

What are Regulating Services?

The benefit provided by ecosystem processes that moderate natural phenomena (eg water purification, decomposition, pollination, carbon storage, climate regulation, erosion control)

What are Cultural Services?

A non-material benefit that contributes to the development and cultural advancement of people (eg. ecosystem roles in local culture, recreation, creativity inspired by interactions with nature)

What is special about the New York City water supply system?

It is the largest UNFILTERED water supply system in the US, serves 9 million people. Water quality is maintained by natural abiotic processes like soil absorption and filtration of chemicals

What is Net Primary Productivity?

gross primary production - respiration = (rate of new biomass appearance)

What effect does the First Law of Thermodynamics have on trophic energy pyramids?

Energy flow decreases along trophic levels in trophic energy periods

What is the Simplified N Cycle?

Huge pool of N2 in atmosphere; smaller pool of C-, H-, or O-bonded N that cycles among plants, animals, soils, solutions; and small set of biologically-mediated transfers between these pools

How has the Global Nitrogen cycle been altered?

Biologically available forms of N are usually scarce under natural conditions, making N a limiting nutrient. Now almost as much N is fixed annually by human-driven processes as by natural processes.

Effects Include:

1. Increases in atmospheric N2O, a potent greenhouse gas

2. Acidification of streams and lakes

3. Increased nutrients in terrestrial ecosystems, potentially leading to changes in species diversity.

What does it mean to fix Nitrogen or Carbon?

Makes inorganic compounds into organic compounds available to living organisms.

What caused the dead zone in the Gulf of Mexico?

Nitrogen and Phosphorous runoff from the Mississippi River, leading to algal blooms which sink and decompose, leading to depletion of oxygen

What effect does rising CO2 level have on the ocean?

It acidifies the ocean, making it difficult for organisms to synthesize calcium carbonate shells (shells can become vulnerable to dissolution)

How do we know what happened millions of years ago?

Scientific evidence - fossils in sedimentary rocks, physical dating methods (radioisotopes, paleomagnetic dating), phylogenetic trees and molecular clocks

What do fossils show?

Fossils deposited over time in sediments show the relative age of organisms

What is Radiometric Dating?

-Radioisotopes decay at a constant rate over time

-When hot rock cools, radioisotope atoms are trapped in place, resetting the radiometric clock.

-When an organism dies, it stops exchanging C with the atmosphere.

-The ratio of radioisotopes to decay products tells us the age of the sample

How do we use Phylogenetic Trees and Molecular Clocks to measure the age of organisms?

We can date the divergence of major groups by reconstructing the history of change in DNA sequences, assuming a constant rate of change.

What are some examples of major geophysical events?

Tectonic events (earthquakes or volcanic eruptions), atmospheric change and altered biogeochemical cycle, climate change, changes in sea level, asteroid impacts, orbital variation

What do Plate Tectonics drive?

They drive continental drift and volcanic activity

What are the periods of time (from oldest to most recent)

Cambrian (~500 million years ago); Devonian (~400 mya); Permian (~250 mya); Triassic (~200 mya); Cretaceous (65 mya); Present Day

What are some effects of massive volcanic activity?

- Ash, SO2 aerosols block sunlight

-CO2 released has longer residence time in atmosphere (greenhouse warming and ocean acidification)

-Other emissions (eg, Cl, F, leads to ozone depletion and acid rain)