BIS 2B UC Davis Midterm 1

Ecology

the study of interactions among organisms and between organisms and their environment.

Ecology's fundamental goal

To assess the biological and physical factors that determine the distribution and abundance of species.

Evolution

A change in the properties of populations of organisms that transcend the lifetime of a single individual.

Species Richness

the number of species in a given area

Species Evenness

The degree to which species are equally abundant

Species Diversity

A measure that combines both richness and evenness

Two types of species

Morphological and Biological

Morphological

Individuals are grouped into species based on their similar appearance.

Pro: Practical and simple to apply, often reflects evolutionary relationships.

Con: Genetic variation within populations, changing morphology in response to environment (plasticity), some species may look similar because they evolved those traits independently.

Plasticity

Changing morphology in response to environment.

Biological Species

Groups of actually or potentially interbreeding individuals that are reproductively isolated from other such groups.

Pro: Clear biological and evolutionary meaning

Con: Difficult to apply in practice. Asexual don't interbreed, reproductive barriers hard to recognize, potential inbreeding doesn't mean actual interbreeding.

Climate average and annual variation in ______ and _______ in a given region over the long-term.

Temperature and Precipitation

What determines Climate?

Incident solar radiation (season and latitude)

Air circulation driven by solar radiation and Earth's rotation.

Hadley Cells

When the sun is directly overhead, the atmosphere is heated causing air to rise, then the air cools. Cool air holds less moisture than warm air, so water precipitates out and falls as rain.

Rain at equator, deserts at 30 N and S b/c of dry air.

Surface winds influenced by

Earth's rotation

Incident radiation also changes with

season

ITCZ Intertropical Convergence Zone

the area of intense rainfall in Hadley Cell circulation

Local variation in climate independent of latitude.

The rainshadow:

Warm moist air goes up the mountain on the windward side, rising air cools and condenses and rains, the dry air cools and sinks on the lee ward side.

Vegetation Changes

Valley Grassland - foothil woodlands - yellow pine - lodgepole - subalpine forest - red fir forest (highest) - woodland - scrub

Populations evolve in response to local climate

Local adaption

Wallace's Line

Biotic interchange and its limits (when the sea levels rise and fall to let animals pass)

Methods of estimation

Floras and Faunas

Extrapolation from sampling number of species in a defined area.

The species - area relationship

S = cA^z

Works for estimating diversity in a single habitat type, but different taxonomic groups and habitats have different 'c' and 'z' parameters.

s=species, c= constant depends on goup, A = area, z= constant determines the shape and slope of the curve (ranges from 0.15 to 0.35)

Threats to Biodiversity

Habitat alteration and destruction

Haresting/Fishing

Climate Change

Introduced Species

Fraction of species remaining =

fraction of area remaining ^z

Sr/Si = (Ar/Ai)^z

Reasons why Biodiversity Matters

1.) Humans depend on species for food, clothing and medicine.

2.) Aesthetic pleasure and the dependence of tourism revenues of biodiversity.

Trade-Off

The relationship between the benefits of a trait in one context and its costs in another context.

Principle of allocation

All life functions cannot be simultaneously maximized.

Bulk of an organism's biomass

Carbon, Oxygen, Hydrogen

Bulk of organisms metabolic machinery (proteins, enzymes, cofactors)

Nitrogen, Phosphorus, macro and micro nutrients

required to run the machinery and build infrastructure (calories)

Energy

Medium in which biological reactions occur

Water

Autotrophs

can live exclusively on inorganic sources of carbon, nitrogen and other essentiial resources.

Photoautotrophs

Use energy from sunlight to power metabolism, growth, and resource-gathering.

Heterotrophs

Use pre-formed organic molecules such as food (source of carbon, nitrogen, energy and other essentials.)

Visible light is ranges

400-700

Visible light is available for

autotrophs to use for photosynthesis

Chlorophyll is a light harvesting pigment of green plants because

It only reflects green and absorbs all other colors.

In addition to carbon, plants need

N (Stunted growth), P, Fe (wilting), k, mg, etc

Heterotrophs: Classified by WHAT they eat.

Herbivores, Carnivores, Omnivores, Detritivores

Heterotrophs: classified by HOW they gather food

Suspension feeder (filter feeder)- remove suspended particles from the water

Deposit feeders - consume dead organic matter

Predator - active hunter of live organisms using and/ or stealth.

Symbiont - Live in with or in another organism and obtain nutrition from that organism.

Symbiont - Parasitic

Benifit comes at the expense of the host

Symbiont - Mutualistic

Host benifits as well

Why specialize (eat few types of prey)?

Evolution of increased efficiency of predation on preferred prey

Why generalize? Eat more types of prey?

Balanced diet, dilute toxins, reduced search costs.

How do generalists choose among different prey?

1.) Effort required to capture and consume prey

-relative size of pretator and prey

-prey defenses

2.) Value of the prey

-energy content

-presence of rare/critical nutrients

-defenses that reduce digestibility

-toxic chemicals

Food choices by animals often _____ net energy intake

MAXIMIZE

Forager Goals

1. Avoid predators

2. find mates

3. Obtain specific micronutrients or vitamins

Without adaptions stress leads to a _______ performance

decreased

Adaption

Evolutionary change in genotype that maximizes performance.

Acclimation

change in phenotype within an individual's lifetime to maximize performance (usually reversible.)

Ectotherms

body temp is determined primarily by external conditions. Lizards.

Endotherms

body temp is determined primarily by metabolic energy. Humans.

Transpiration

Evaporation of water through the stomata keeps leaves from over-heating.

Adaptions that reduce water and/or heat stress in plants

Traits that decrease water loss or heat load:

-waxy covering to leaves

-small vertical leaves

-Low SA/V

Wilting

-Shedding

Reduced stomatal density or opening.

Traits that enhance water supply:

-deep tap roots

-storage of water during times of plenty

Through the stoma

H20 vapor diffuses out of the leaf and CO2 diffuses into the leaf.

Steeper the gradient the faster the diffusion.

Alternative photosynthetic systems

-Alter the CO2 gradient

-Change the timing of the stomatal opening.

C3 Photosynthesis

The most ancient and common system:

Photosynthesis takes place in the mesophyll cells. W/ rubisco.

-Perform better at lower temp

Rubisco enzyme

has a weak affinity for CO2 so stomata stay open longer and much water is lost per C gained.

C4 Photosynthesis

Evolved later and is more water-efficient.

-spatially seperate uptake of CO2 and its fixation.

-PEP carboxykase enzyme is more efficient at grabbing CO2, so C4 plants keep stomata open for less time.

-Inefficient at low light

The niche

the set of environmental conditions (temp, moisture, salinity) under which individuals of a species can grow and reproduce.

Probability of being eaten

P(detection) x P(capture) x P(consumption)

Avoiding detection

-Burrow

-Camouflage

Two costs of being cryptic:

1.) tied to particular habitats

2.) Limited mobility

Greenhouse Effect

Atmospheric "blanket"containing greenhouse gases

Problems with the positive CO2 view:

-Increading CO2 leads to warmer temps.

-this leads to increased transpiration

-changes in temp may change precipitation

-other things limit photosynthesis besides carbon

Population

Collection of organisms of the same species living in the same place at the same time

Exponential population growth

The per-capita growth rate is constant or density independent

Logistic population growth rate

(asymptotic) the per-capita growth rate varies with population density or is density dependent.

Open population

# change due to I and E and B and D

Closed Population

# change due to only B and E

A population ______ in size when its birth rate exceeds its death rate

Increases

B>D

or when r is positive

Density independent limitations

agent of mortality is not triggered by population density (extreme weather)

Density dependent regulation: per individual birth and death rates DEPEND on density

-Decreased per individual birth rates (fecundity)

-Decreased individual growth (fewer offspring)

-Increased death rate

(resource depletion, predators, disease, dispersal)

Carrying capacity (K)

the maximum population size that can be supported by available resources or physical space.

Population growth

equals the amount expected under exponential growth multiplied by what percent of the carrying capacity is left.

If N is very close to k

then population growth will be slow.

If N is very small relative to K

then growth will be nearly exponential.

If N is very large compared to K

then growth will be logistic and go back down to the K

r-selected species

High intrinsic rate of population growth

traits that are successful when densities are far from K and popn growth is driven by r.

(early reproduction, large # of offspring w little parental care, etc.)

K-selected species

traits that are favored when population sizes are near K

(large investment in few offspring, continuous reproduction...etc.

The principle of allocation:

there is a tradeoff between the number of offspring and investment per offspring.

Attributes of r - selected

Many, small highly dispersed offspring, small body size, short life, early reproduction, allocate rapid growth and high reproduction, little parental care, semelparity (reproduce one time before death)

Attributes of K-Selected

Fewer, higher quality offspring, large body size, long life expectancy, delayed reproduction, allocate to defense, persistence, high parental care and investment, Iteroparity (reproduce many times before death)

Environmental conditions favor for r - selected

Keep populations are low density, habitat is unpredictable, variable, harsh, disturbed, mortality IS independent of other organisms and often catastrophic.

Environmental Conditions favor for K-selected

Populations can reach high density, habitat is predictable, favorable for growth and survival, mortality is often caused by interactions with other organisms.

How to get r estimate

Direct method:

-Follow a cohort (group of individuals born at about the same time) through time

Indirect Method:

-Determine the age of death from remains

Fecundity

(mx) avg # of offspring produced by individual of age x.

Net reproductive rate (R0)

avg # of offspring produced by an individual during its entire lifetime.

R0 = Ixmx

R0>1

increasing

R0<1

decreasing

The earth is

4.5 billion years old

Life has been around for

3.5 billion years

All life on earth has descended from

a single ancestor

The degree of resemblance among organisms corresponds to their

relatedness

Resemblance among relatives is due to inheritance of discrete genes

1.) individuals differ, even close relatives

2.) the magnitude of the difference between relatives reflects time since they shared a common ancestor.

Homology

Correspondence among parts is due to descent with modification.

vestigial organs: why do organisms have them?

Historical baggage/evolutionary legacy.

Uniformitarianism

Canyons and other major geological features on Earth are gradually formed by slowly acting processes accumulating over long periods of time.

Charles Lyell

geological uniformitarianism

Uniformitarianism to Darwin

-He thought evolution was too slow to be directly observed.

- But if evolution operated over long periods of time, then small changes could accumulate.

Organic Evolution Defined

All living things have developed from pre-existing common ancestors.