BIO 1B-ECOLOGY

Principle of Allocation

Individual organisms have a limited amount of resources to invest in different activities and functions. Resources invested in one function are not available for another (a trade off).

In life cycles, resources must be allocated among growth, survival, and reproduction

Trade-Off

Species can have more smaller or fewer offspring

Survivorship

Fraction of individuals surviving to a given age

Type 1 curve

Most individuals reach old age (Humans)

Type 2 Curve

Some individuals reach old age- linear curve (birds)

Type 3 curve

Very few individuals reach old age (plants)

Fast-Slow Continuum

Some life-history traits are coordinated along a "fast-slow" continuum. Fast species are often smaller and slow species are often larger

Life history

suite of traits related to a species' life cycle and timing of major events

e.g: average lifespan, age at first reproduction, size and number of offspring in each episode

Costs of Production

More production in one year means less reproduction the next year

Birth and Death Model

The number of individuals in a population at time t. Accounts for each of: birth, immigration, death, and emigration

N t+Δt = Nt + B + I -D - E

Exponential Model

Describes how a quantity increases over time, where the rate of growth is proportional to the current value, leading to rapid increases.

- No density dependence

Logistic Model

Population expansion decreases as resources become scarce, leveling off when the carrying capacity of the environment is reached, resulting in an S shape

Per capita population growth rate

Rate of population growth divided by population size. A metric of the average rate of population change for an average individual in the population.

1/N x dN/dT = r(1-N/K)

Density Dependence

Changes in per-capita population growth rate with population size

+ density dependence (slope is +)

no density dependence (slope is constant)

- density dependence (slope is -)

Carrying capacity (K)

-A constant number, not a variable

- the population size at which N comes to equilibrium

- population comes to equilibrium when N=K

Intrinsic growth rate (r)

- a constant number, not a variable

- describes how quickly population size will increase starting at a very low density

Population Flucuation

Populations go up and down over time, and does not match exponential or logistic model

Can exponential growth continue forever?

Growth slows down as populations become denser. We would need a more complex model to describe reality. Our assumption is that every individual in a population has an equal chance of reproducing and dying. Populations eventually stop growing.

Why is negative density dependence common?

Life is more challenging in denser populations, reducing birth rates and increasing death rates

- fewer resources per individual

- more competition among individuals

- fewer available mates

-more disease/parasites

-more predation risk

intraspecific competition

competition between individuals of the same species. Is the mechanism behind density dependent population growth

Interspecifc competition

competition between individuals of different species

Herbivory

One species eats part (or all) of another species, which is a plant. The plant may or may not die, so herbivory is sometimes but not always predation. Usually a negative impact on the plant but not always

Parasitism

One species (the parasite) lives inside or on another species and benefits, but in return harms the species (the host) it is living in

Mutualism

Both species benefit from the interaction. Many possible mechanisms

- disperse seeds

- pollinate flowers

- defend against herbivores, parasites, and predators

Commensalism

A type of facilitation. One species benefits, and the other is unaffected

e.g. a remora and its host, a zebra shark

facilation

one species benefits another. Typically not specified whether the second species is impacted, but often the impact is positive

Defense

Prey defends physically, defends chemically, or physically escapes the predator

Dishonest mimicry

Looks like the species but doesn't have to work for similar affects

Honest mimicry

appears like an unpalatable species, and is unpalatable

Exploitation competition

Populations can indirectly interact even if individuals do not directly interact

e.g. species A and B eat the same prey C. If A eats C better, B suffers

Indirect mutualisms

ABC are herbivoired by Species D, and both A and B are less palatable to D, so C is a more attractive target, therefore A and B help each other

Interaction Network

Diagram with arrows linking species that have a direct pairwise interaction

Coevolution

A reciprocal evolutionary change of two or more species interacting with one another, where the activity of one species influences the evolution of the other

Species interaction (type 1)

an individual of species A influences the behavoir or life events of an individual of species B

Species interaction (type 2)

an individual of species A influences growth, survival, or reproduction of individual species B

Species interaction (type 3)

a population of species A influences the growth rate (dN/dT) of a population of species B

Competition

occurs when two or more individuals share a resource, and consumption by one reduces it availability for others, causing reduced growth, survival, or fecundity (- effect on both species)

Community

multiple species co-occuring in a place at a time, and possibly interacting with each other

Coexistance

Species in a community are able to live alongside one another in the same place or at the same time, but this could be a positive or negative interaction

Scarcity

Fundamental niche

The full range of conditions or resources used in which a species could maintain a stable population in the absence of other species; niche limits are based on physiological tolerance limits and resource needs

Realized niche

the actual set of conditions or resources used in which the species could maintain a stable population in the presence of other co-occuring species; limits usually set by competition/predation or other negative limits

Niche partitioning

Each species has the same fundamental niche

Each species has a different realized niche

Competition is reduced through each species occupying a different realized niche

Niche overlap

More niche partitioning, less competition, greater coexistance. Character displacement reduces niche overlap

Predator/prey system

Species do not share a resource, one is the resource for the other.

Scenarios:

-predator eats all of the prey, so they both go extinct

-predator cant find any prey, so predator goes extinct and prey populations increase

-they coexist with one another

Spatial refuge

a habitat feature or specific area that provides organisms protection from environmental stressors

Disturbance

a change in abiotic or biotic conditions in a community

- changes in weather

- species introductions

- species exclusion or extinction

Primary Succession

Following a disturbance, the community becomes empty, or basically empty. Any species that enters the community must first immigrate from another

Secondary Succession

Following disturbance to an existing community, population decline or only individuals of some life stages survive (seeds, spores)

Initially-arriving species

(early-successional) are outcompeted by later arriving (late-successional species); early species may also faciliate late species by improving soil nutrients

Competitive exclusion

Negative species interactions can have slow impacts on populations

Species richness

the total number of species

Species eveness

Relative similarity in abundance of species

Species composition

Identities for which species are present

Spatial grain

the characteristic scale at which measurements are reported

Spatial extent

The overall region in which the measurements are made at the selected spatial grain

Latitudinal diversity gradient

Pattern of changes in species richness with latitude

Generally highest species richness is near equator, lower richness towards North/South Pole

Observed to exist across taxonomic groups

Higher biodiversity levels in tropical regions vs polar regions

Leading explanations for LDG

- More land to support more species

- Environments are less stressful in tropics meaning more species survive

-more annual solar radiation, therefore more energy

- higher temperature-> higher mutation rates-> species rates

Island biogeography theory

-Islands that are closer to mainland get more immigration

-larger and closer islands have higher biodiversity rates

Luxury effect

the positive correlation between wealth and biodiversity in urban areas, where wealthier neighborhoods tend to have higher plant and animal diversity and access to biodiversity

Species area relationship

Larger areas tend to support more species than smaller areas

Species distribution

A species range of where it is typically found. Climate, habitat, resource availability affects this

Dispersal

the movement of individuals or gametes away from their original location

- mobile organism

- wind

-water

- biotic vector

-abiotic vector

Dispersal limitation

Often dispersal limits species distributions and is limited by behavoir

e.g. birds can fly long distances, but are scared of predation

- blue whales move to avoid shipping risk

Abiotic limit

Non-living components of the environment

limit: temperature

Biotic limit

Living components of the environment

Limit: Herbivory, competition

Environmental gradient

Species limits are set by environmental gradients which can be multiple things

-temperature

-elevation

-storm risk

-predation risk

Biome

a region experiencing similar environmental conditions and therefore containing a similar 'core' set of species

Hadley Cell Circulation Recipe

1. Tropical air heats up, moisture rises and air cools

2. Cooler air precipitates moisture as rain in tropics

3. Rising air is displaced either north or south, creating winds and air transport

4. Transported air begins to cool down and sink

5. Dry air falls in mid-latitudes

How does the Earth's physical structure influence the climate conditions that then in turn influence where species are found?

-role of temperature: temperature increases at low latitudes because they receive more solar radiation

-role of precipitation: Precipitation decreases at mid-latitudes because of the Hadley Cell circulation

Why are mountain tops colder

Because when air rises, it expands. When it expands, it has a lower density and pressure

Maritime climate

Oceans buffer climate, so climate extremes are stronger on the interior of the continents

- giant reservoir of heat

- water warms and cools slowly

Photosynthesis

solar energy is captured by formation of carbon bonds in compounds that are stored in organismal bodies

Respiration

metabolic reactions release chemical energy, in doing so return carbon to the environment, and re-radiate thermal energy

Gross Primary Productivity

all the energy obtained from sulight by autotrophic organisms

Net Primary Productivity

all the energy available to other organisms from autotrophs

NPP= GPP-R

R-respiration

Where is NPP the highest?

Oceans

tropical forests

Climate drivers of terrestrial NPP

Plants lose water in exchange for gaining carbon in photosynthesis: water availbility is a limit on productivity

What happens to energy flow between trophic levels?

-Energy transfers through trophic levels

-Efficiency is lost from each level

Ecological efficiency

fraction of energy later available to other organisms as growth

Assimilation fraction

fraction of energy used by an organism for growth and respiration

Distribution of energy across trophic levels

Because of the 10% average ecological efficiency, trophic pyramids are common- less biomass/energy in higher trophic levels

There has to be more plants than secondary consumers

Bottom-up control

Amount of limiting resources determine energy available to producers, which in turn limit other trophic levels

Top-Down control

Amount of top predators/consumers determines energy flows of prey, which in turn limits other trophic levels

Sociometabolism

metabolism of humans accounting for bodily use and also indirect consumption through appropriation of ecosystems as well as other energy sources

Flux

rate of movements between compartments

Stock or pool

Amount in the compartment of the system

Residence time

How long something spends in a compartment if the system is at equilibrium

Residence time = stock/flux

Sink

a stock that is increasing due to a net flux

net flux (add up all the arrows going in and subtract the arrows going out)

Source

a stock that is decreasing due to a net flux

Carbon cycle processes affect atmospheric CO2

All fluxes to/from the atmosphere affect the stock of atmospheric carbon, which is mostly CO2

Atmosphere is not at equilibrium: flux to atmosphere is greater than flux from the atmosphere, meaning the carbon stock in the atmosphere is increasing

Haber-Bosch Process

Nitrogen fertilizer production

Production of nitrate from nitrogen gas using catalysts, hydrogen, and high pressure/temperature

Made possible by availability of inexpensive fossil fuel energy

Nitrogen fixation

Atmospheric nitrogen is converted into usable forms like ammonium/ammonia and nitrates by microoganisms

Chemical fertilizer

Manufactured using the different proportions of major chemical nutrients, such as nitrogen and phosphorus

Rock weathering

Phosphorus comes from rock weathering, which is then taken up by organisms, then runs into the ocean and is lost from terrestrial organisms

How do humans increase nitrogen inputs

By industrial nitrate fertilizers, acid rain, which is primarily driven by chemical reactions arising from fossil fuel emissions

Dust transport

Dust particles that are carried by wind to various locations and distances away from the original source and deposited back onto the surface somewhere downstream

Stocks and flows of Phosphorus

Rock sources provide the majority of phosphorus inputs to land

inputs have increased by 66x from the 60s

large amounts of P are lost to the ocean permanently due to agricultural runoff

phosphorus use is rapidly increasing due to agricultural production

Greenhouse gas

types of gases that absorb infrared radiation and reemit infrared radiation, trapping more of the gases in the atmosphere instead of allowing it to radiate to space- may contain carbon, but others not. They act like a planetary blanket

Key greenhouse gases

-CO2

-N20

-Methane Ch4

-Ozone

-Water Vapor