bio 1b mid 2

Population

A group of individuals that belong to the same species and live in the same area

Community

All the different populations that live together in an area

Ecosystem

A biological community of interacting organisms and their physical environment.

Biosphere

part of Earth in which life exists including land, water, and air or atmosphere

life history

Traits that affect an organism's schedule of reproduction and survival.

principle of allocation

the observation that when resources are devoted to one body structure, physiological function, or behavior, they cannot be allotted to another

Trade-off

Resources invested in one function are not available for another

Survivorship

the percentage of members of a group that are likely to survive to any given age

fast-slow continuum

hypothesis says that a species can be arranged along a continuum from high to low adult mortality.

What is an example of a community you could find at the beach?

Different species of birds; or different species of organisms living in a tidepool

Why can organisms usually not simultaneously maximize performance of different functions?

There is an allocation tradeoff - a finite amount of resources cannot simultaneously be used to maximize all functions (e.g. if you have $10 you can't spend $8 on one item and also spend $8 on another item)

What are examples of slow life history traits or organisms?

Long lifespan, late reproduction, few reproduction events; large body size, low mortality rate. Examples include elephants, sequoia trees, large fish like tuna.

Why might species with parental care be more likely to have Type 1 survivorship curves?

Parents can care for offspring, limiting juvenile mortality. This process effectively keeps the survivorship curve high over a wide range of ages.

Fast life history traits

Reproduce early, small body, small brain, short gestation, large litters, high mortality rate, short life span.

Type I curve

most individuals survive to old age

Type II curve

Some individuals reach old age

Type III curve

Very few individuals reach old age

birth

being born

death

end of life

Immigration

Migration to a new location

Emigration

Migration from a location

B-D model

the size of a population in a given year is the size in the previous year plus the number of new individuals born and minus the number of individuals that died

exponential model

a model of population growth in which a constant and unlimited growth rate results in geometric increases in population size

logistic model

a model of population growth that assumes that finite resource levels limit population growth

per capita population growth rate

rate of addition of individuals per individual in population

Density dependence

regulation of population growth by mechanisms controlled by the size of the population; effect increases as population size increases

equilibrium population size

b=d

carrying capacity (K)

Maximum population size that a particular environment can support.

Instrinsic growth rate (r)

the maximum potential for growth of a population under ideal conditions with unlimited resources

Population fluctuation

Variability in population size over time.

Nt+deltat = Nt + B + I - D - E

Nt = initial pop size, delta t = change in time, B = births, I = immigration, D = deaths, E = emigration

Why are population growth rates useful for determining species distribution limits?

Species are not present in locations where their population growth rate is negative. Thus mapping population growth rates in different locations lets us map species range limits.

What restrictive assumptions are made to derive the geometric and the exponential population models?

We assume that there is no immigration or emigration, and that there is a constant rate of population increase that does not depend on the environment, or on the density of the species (i.e. big and small populations grow at the same per-capita rate).

How can you estimate r or rdelta from a graph of population size vs. time?

For exponential growth, the slope of the line (on logged y-axis scale) is the value of r. For geometric growth, the slope is the value of 1+rdelta.

Does exponential growth mean a population is always increasing?

No, it depends on the value of r. If r is zero the population is constant, and if r is negative, the population is shrinking.

What units does r have?

The units are number per unit time.

Why can populations not increase forever at exponential rate?

Eventually some factor becomes limiting to growth, and the existing population experiences a negative feedback that reduces population growth rate. For example a finite amount of resources will ultimately lead to fewer resources being available to each individual.

What are examples of density-independent vs. density-dependent factors influencing a population?

Independent: volcano eruption, change in climate (e.g. temperature), bulldozing. Dependent: resource competition, fire (if denser tree populations mean hotter/more deadly fires), disease (if disease spreads easier in denser populations).

In the logistic model, what does the plot of per-capita population growth rate vs. N look like, and how does it compare to the plot of population growth rate vs. N? Biologically, how do you interpret these graphs?

The per-capita population growth rate plot is a straight line that has negative slope that crosses the y-axis at N=K. The population growth rate plot is a parabola that crosses the y-axis at N=0 and N=K, with maximum at N=K/2. The parabola arises because of the balance between greater growth rates in larger populations (r*N) and the reduction in growth rate due to density ((K-N)/K).

intraspecific competition

competition between members of the same species

interspecific competition

competition between members of different species

Predation

An interaction in which one organism kills another for food.

Herbivory

interaction in which one animal (the herbivore) feeds on producers (such as plants)

Parasitism

A relationship between two organisms of different species where one benefits and the other is harmed

Mutualism

A relationship between two species in which both species benefit

Commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected

Facilitation

An interaction in which one species has a positive effect on the survival and reproduction of another species without the intimate association of a symbiosis

defense

Fighting off predators physically or chemically

Dishonest mimicry

appears like an unpalatable species, even though it is palatable

Honest mimicry

appears like an unpalatable species, and is unpalatable

exploitation competition

organisms compete indirectly through the consumption of a limited resource

indirect mutualism

when the indirect interaction is beneficial to both species

Interaction network

can be used to analyze all types of biotic interactions in a community/ecosystem

What kinds of interactions can be + for one species and - for the other species?

predation, herbivory, parasitism

Can you think of interactions that do not occur for species pairs but do occur for species triplets? We didn't cover this in class, but see if you can come up with an example.

If species A is a predator, and species B/C are prey, A may switch to preferentially eating B when C is present. Or A, B, and C are microbes, A may secrete an antibiotic that harms only B, but the effect of the antibiotic may be diminished if C independently secretes another compound that inactivates the antibiotic.

What strategies do you think squirrels use to prevent being predated by hawks or falcons?

Squirrels are camouflaged (dark colored) to blend in as a hiding strategy. They also can run from predators. They can also associate with other species like humans that dissuade predators from hunting them.

Think of an example of mutualism involving fish.

A clownfish lives in an anemone. The clownfish gets a safe place to live because the anemone stings other species. The anemone gets protection against predatory fish like butterfly fish because the clownfish will chase them off.

What are ways in which individuals of a woodpecker bird species might compete with each other?

Competition for insects (food), competition for mates, competition for nesting sites in trees, competition for territories to hunt for insects.

coexistence

When two species share the same fundamental niche and live together, but neither species goes extinct.

Scarcity

A situation in which unlimited wants exceed the limited resources available to fulfill those wants

competition

the struggle between organisms to survive in a habitat with limited resources

fundamental and realized niche

Fundamental niche is the entire set of conditions under which an animal (population, species) can survive and reproduce itself. Realized niche is the set of conditions actually used by given animal (pop, species), after interactions with other species (predation and especially competition) have been taken into account.

niche partitioning

natural division of resources based on competitive advantages

niche overlap

When species must compete with others for the same resources

Predator-Prey System

Dynamic interaction between predator and prey populations.

cycle

A series of events that happen over and over again.

spatial refuge

physical locations where prey are outside the reach of predators

fluctuation

rise and fall, continual variation

disturbance

an event, caused by physical, chemical, or biological agents, resulting in changes in population size or community composition

Primary / secondary succession

Tend to increase biodiversity; increase species richness and interactions among species

What is a community? What are examples of communities, and what are not examples of communities?

A community is a set of organisms that co-occur in a given place and time. They may or may not interact with each other. All the fish and insects and microbes in a lake is a good example of a community. The rocks and air near a mountain is a bad example of a community (no organisms). The polar bears all across the world is a bad example of a community (no specific place).

Why is scarcity a fundamental concept for thinking about ecological competition?

When resources is scarce, organisms cannot obtain as much of it as they need and are limited in their fitness by the resource. This leads organisms to change (via behavior, ecological distribution, evolution) to improve fitness. Competition for resources occurs as not all organisms can all obtain a full allocation of resources. This also leads to tradeoffs as organisms may need to give up other things to be able to gain resources.

What are ways in which individuals of a woodpecker bird species might compete with each other?

Competition for insects (food), competition for mates, competition for nesting sites in trees, competition for territories to hunt for insects.

How could you describe the realized niche of a Berkeley campus squirrel?

Realized niche: temperatures perhaps between 40-90°F, rainfall 5-10x/year, seeds or nuts of size 1 mm - 5 cm (can't eat anything bigger than that), presence of trees with height > 3 m (these particular values are just guesses, but these types of axes are what you should be thinking of).

Why does niche partitioning reduce competition and promote coexistence?

When organisms use different resources, resource scarcity is alleviated and there is less need for competition.

Can a realized niche be larger than a fundamental niche?

Yes, potentially - for example for organisms that depend on others to exist (e.g. symbionts), or that are able to use more habitats than they would otherwise (e.g. plants in the desert that rely on other larger plants for shade/cooling)

What are examples of disturbances that could affect a stream ecosystem like Strawberry Creek in Berkeley?

Rainfall events can change streamflow and chemistry. People playing in streams (or dogs) can change the physical conditions. People dumping chemicals into streams can change their chemistry. Earthquakes can change streamflow and introduce rocks and debris into streams.

In Earth life were somehow transferred to Mars (maybe via the crash of a space probe?), would this be an example of primary or secondary succession?

This would be primary succession because the organisms colonizing the location have come from a long distance away rather than re-establishing from nearby.

Describe what happens when you take a probiotic pill from the perspective of succession.

In this case the resident microbial community in our gut is invaded by new species in the probiotic pill. The new species may potentially establish and shift the community composition, potentially allowing further long-term shifts in community composition that hopefully benefit our health.

species richness

the number of different species in a community

Species evenness

relative abundance of each species

species composition

The identity of the species present in a community.

spatial scale

the different sized "containers" or ways to group places together to organize investigations into human activities

species-area relationship

species richness increases with area sampled

island biogeography theory

explains how species come to be distributed among oceanic islands

equilibrium richness

reached once immigration and extinction cancel each other out

luxury effect

richer people have more access to biodiversity

latitudinal diversity gradient

the increase in species diversity from the poles to the equator

What is the difference between richness and evenness?

Richness describes the total number of species; evenness describes whether individuals are allocated in the same abundances among species, or if some species are much more abundant than others.

If you increase the grain size of a biodiversity map, would you expect to see more or less spatial variation in biodiversity?

You would see less, because each location averages out more of the variation when the grain size increases.

If you measured 100 species of plant species in the entire Berkeley campus, is 200 species a good guess for the number of plant species in an area twice the size of the Berkeley campus?

It is a bad guess. We know that doubling an area leads to less than double an increase in richness, because the SAR slope on log-log coordinates is less than one. This should make sense because if we double the search area we are likely to re-encounter some of the same species we have already found in the first search area.

Which Hawaiian island would you expect to have the highest species richness according to the island theory of biogeography?

All else being equal, the Big Island - it is closest to the mainland of North America, and it is also the largest, so it probably has the highest immigration rate and the lowest extinction rate. (Note in reality the story is more complex because of the volcanic history of the islands and their differential evolutionary histories!)

Based on the global maps of species richness we saw in lecture, what other factors besides latitude might affect biodiversity?

There seems to be peaks in biodiversity in places with mountain ranges (e.g. the Andes, the Himalayas). Thus elevation, or variation in elevation, might also be important.

species distribution

areas of the world in which a species lives

dispersal

the movement of organisms from one place to another

dispersal limitation

the absence of a population from suitable habitat because of barriers to dispersal

environment

the surroundings or conditions in which a person, animal, or plant lives or operates.

Biotic limit

Ability to survive/reproduce limited by interactions with other species, predator and herbivory, presence/absence of pollinators, food resources, etc

Abiotic limits

Ability to survive limited by chemical and physical factors including temperature, performance curves

behavior

The way an organism reacts to changes in its internal condition or external environment.