Bio 1B MT2

Principle of Allocation

Limited resources must be allocated between growth, survival, and reproduction (example: animals forage, breed, care for offspring. Plants allocate biomass and nutrients to different parts like root, stem, etc)

A Trade-Off

Resources invested in one function are not available for another (an adaptation or trait that improves fitness in one area comes at the cost of another area due to limited resources) Example: species could have more smaller or less bigger offspring

Survivorship Curves

Type I: most reach old age (humans)

Type II: some reach old age (squirrels)

Type III: very few reach old age (plants)

Fast-Slow Continuum

Fast species tend to be small, while slow species tend to be large (many exceptions exist)

Case Study: DDT

DDT was used as a insecticide in the 1900s, caused eggshell thickness issues for many bird species, especially bald eagles

Demography

Study of how a population changes over time

The BIDE Model

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

Nt=number of individuals in a population at time t

Birth, Immigration, Death, Emigration

Simplified Version (assuming closed population): Nt+deltat=Nt+B-D

Population Growth Assumption

every individual has an equal chance of reproducing and dying

dNt/dt = b-d = rNt

r=each individual’s net contribution to the population

Exponential Growth Model

Nt=N0 x e^rt

N0 = initial number of individuals

r = intrinsic growth rate

When r is positive, the population increases, when r is 0, the population does not change, when r is negative, the population decreases

Per Capita Population Growth Rate

(1/N)(dN/dt)

Rate of population growth divided by population size, measures average rate of population change for a single individual

Density Dependence

Positive: per-capita population growth rate increases

Negative: per-capita population growth rate deceases

0: Equilibrium (b=d)

Logistic Model

(1/N)(dN/dt) = r (1-(N/K))

r = constant

K = carrying capacity

Population comes to equilibrium when N=K

(1/N)(dN/dt) is greatest when N is near zero

Density Independent

Sometimes, N is limited by something else and fluctuates (ex. volcano eruption impacts forest tree populations)

Competition

Species A and B try to acquire the same resources

Intraspecific: competition between individuals of the same species

Interspecific: competition between different species

Predation

Predators reduce prey abundance, so prey defend physically, chemically, escape, mimicry (honest: appears unpalatable, is unpalatable; dishonest: appears unpalatable, is palatable), fight back

Herbivory

Eating plants (the plant might or might not die, so it is only predation sometimes)

Usually a negative impact, but sometimes it could be beneficial

1. A cost paid to support mutualism (seeds eaten by squirrels who also disperse them)

2. Regular disturbance that removed dead tissue and reduce disease

3. A signal that promotes growth

Mutualism

Both species benefit (ex. disperse seeds, pollinate flowers, defend against parasites, gather nutrients, etc)

Facilitation

One species benefits another, the second species is unspecified, also called mutualism for plants (ex. host plants facilitate other plants growing inside them)

These interaction could shift from competitive to mutualistic as elevation or other stress increases

Fungus and soybean is competition in low phosphorus, mutualistic in medium phosphorus levels, and fungus becomes parasitic in high levels

Commensalism

One species benefits, the other is unaffected (ex. remora and host, a zebra shark)

Indirect Interactions

Exploitation Competition: two predators eat the same prey

Indirect Mutualism: plant A and B help each other when C is most palatable

Human Interactions

Agriculture, livestock, unintentional introduction of new species

Coexistence

Species can coexist in the same location if they don’t compete for the same resource

Fundamental Niche

Full range of condition or resources that a species can survive in (doesn’t take into account other species in the area)

Realized Niche

The actual set of conditions that the species live in the presence of other species (ex. birds separating into different level of the same tree due to competition)

Niche partitioning

Separation of niches: more niches partitioning, less competition, greater coexistence

Spatial Refuges

Simple environment: no refuges for prey, predator kills prey, then goes extinct

Complex environment: refuges for prey, prey is killed, but can survive in other places enough to escape predator

Disturbance

Any change in abiotic or biotic conditions (change in weather, new species, extinction)

Primary Succession

Community is empty, needs immigration to start again (ex. glacier retreat)

Secondary Succession

Populations decline but does not die out. Early-successional species are outcompeted by late-successional species

Scales of Diversity

Spacial Grain: characteristic scale (ex. 1×1 meter rectangle) Increase grain size=reducing pixel size

Spacial Extent: the overall region (an entire state) Increase extent=increase area of interest

Abundance

Number of individuals

Richness

Total number of species

Evenness

Relative equal distribution of all species

Composition

Identities of which species are present

LDG

Latitudinal Diversity Gradient

highest species richness near equator, lowest at the poles because more land area, less stress, more sun, higher temp, more time since no ice

Factors that increase richness over time

longer evolutionary time, larger area (island biogeography theory-larger and closer to mainland islands are better), longer time since disturbance, more indigenous land use, less poverty

Factors that decrease richness over time

More agricultural intensification (pesticide use), more land clearance (oil palms)

Agroforestry Systems

Maintain higher biodiversity than plantation agriculture, keeps natural landscape fragments, can also present TEK and cultural practices

Species Distribution

Affected by dispersal, abiotic/biotic, human activity, and behaviors

Dispersal

Movement of individuals and gametes to and from their original location

Often limited by behavior (birds refuse to cross gap due to fear of predators)

Abiotic and Biotic conditions on distribution

Abiotic: temperature and heat tolerance

Biotic: herbivory by cattle or competition between species

Environmental Gradients

Temperature, elevation, hurricane, predation risk gradients (could be continuous or patchy)

Biomes

Region experiencing similar environmental conditions and support a similar set of core species (Mojave and Sonoran Deserts), depends on climate, precipitation

Temperature Differences

Due to less sun at higher latitudes and more at lower latitudes, elevation causes air to expand and cool, less seasonality (cooler summer, warmer winter) near oceans

Precipitation Differences

Hadley cells leads to the tropics (mid-latitudes) to receive more rain, windward side of mountains facing ocean gets more rain than rain shadow on leeward side

NPP

NPP=GPP-R

NPP=net primary production

GPP=gross primary production

R=respiration rate

Climate drivers: water availability, extreme temperatures

Ecological Efficiency

Fraction of energy available to other organisms, average is 10%, causes trophic pyramids

Assimilation Fraction

Energy used by an organism for its own growth and respiration

Trophic Cascade

Bottom-up: limited resources determine producers and in turn upper trophic levels

Top-down: top predators determine energy flow and in turn lower levels

Metabolic rate of average person vs average plant

120 W, 4 W

Sociometabolism

Metabolism of humans accounting for bodily energy use and also indirect consumption such as agriculture, raising animals, burning biomass, fossil fuels, etc

Stock/Pool

Amount in the system

Flux

Rate of movement between compartments

Residence time

How long something spends in a equilibrium system (input=output), =stock/flux

Sink and Sources

Sink: positive net flux, increases

Source: negative net flux, decreases

Carbon Cycle

Atmosphere is not at equilibrium: net flux is positive, means greenhouse gases increase

Humans: fossil fuels burning (bigger impact), land use change (deforestation)

Nitrogen Cycle

Nitrogen builds DNA, RNA, ATP, etc.

Nitrogen reaches animals and plants through nitrogen fixing bacteria or decomposers (nitrogen gas into ammonium, nitrates), nitrogen escapes animals and plants through decomposers and denitrifying microbes

Humans increase nitrogen inputs via nitrogen fertilizers and acid rain

Hager-Bosch Process

Production of nitrate from nitrogen gas using fossil fuels, humans contribute 51% to nitrogen flux

Alternatives to fertilizer

Nitrogen fixing crops used as polyculture, or crop rotation (beans and peanuts)

Phosphorus Cycle

Phosphorus comes from rock weathering and phosphate rock formation, humans also input large amounts for fertilizer

Greenhouse Gases

Absorb IR radiation and re-emit it, trapping heat. CO2, N2O, CH4, O3, H2O

Positive Feedback Loop

More and more: ice feedback(warming, more ice melts, lower sunlight reflected albedo, more warming), vegetation feedback (warming, more trees die, less CO2 absorbed, more warming), cloud feedback 1(warming, more high altitude clouds, more IR absorbed, more warming)

Negative Feedback Loop

More leads to less: radiation feedback (warming, more IR radiation emitted, more cooling), cloud feedback 2 (warming, more tropical altitude clouds, more sunlight reflected to space, more cooling)

Deforestation causes drought

Less plants, more runoff, less aquifers, drier conditions downwind

RCP

Representative Concentration Pathway: scenarios that make predictions such as global warming and CO2 levels based on different trajectories of population growth, economic development, and carbon efficiency

Climate Change

Hot places get hotter, polar will get hotter, dry places get drier, wet places get wetter

Novel climates can push species beyond fundamental niche (range shifts)

Effects on humans: More extreme weather events, changing crop yields

Phenology

Changes in timing of seasonal events relating to organisms, often due to climate change

Disease

genetic, immune, diet, developmental, physical, environmental/chemical, infectious

Biological pest control

Use wasps to kill caterpillars on cotton instead of insecticide

Gene drive

Introduce infertility mutation into mosquitoes to cause extinction

Disease ecology used in biological warfare

Rinderpest (disease of cattle), Smallpox (disease of humans), cover smut (fungal disease of wheat), “Agent Orange” (mixture of herbicides)

Organisms can cause diseases

Algal blooms, secrete toxic compounds into water

Parasites, feeds and lives on a host and causes harm

Pathogen, a organism or virus that causes disease but not living in host

Transmission of Pathogens

Contact (direct movement from one host to another), vehicle transmission (indirect via water, dust, aerosols), vector transmission (indirect via another species)

Janzen/Connell Effect

Diseases/enemies that increase when their hosts have high-density populations cause negative density dependence (prevents host species from becoming very large in population)

Metapopulation

Patches each with populations that are linked by immigration/emigration. Diseases spread as metapopulations, and can re-emerge from other patches even if it’s gone from other patches.

Reservoirs for pathogens

Environmental: location where pathogens live when they are not parasitizing

Biotic reservoir: location where pathogens live when they are parasitizing

Zoonotic disease: diseases that normally don’t affect humans but could be transmitted (Lyme disease)

SIR Model

Susceptible → infectious → recovered (or dead)

Epidemic occurs if infectious individuals starts to increase (dl/dt>0)

dI/dt = beta*S*I - m*I

beta=transmission rate m=recovery rate S=number susceptible I=number infected

(S*beta)/m = R0

R0=1: epidemic stays the same size R0>1: epidemic grows R0<1:epidemic shrinks

Many exceptions are more complicated than SIR model, like bubonic plague

Global changes that increase disease spread

Habitat destruction, urbanization, air travel, climate change

Indigenous fire management

Regular burning to promote habitat for food plants, game animals, etc. US uses fire suppression instead, that causes greater forest densities and larger fires

Pyromes

Fire-dependent biomes: Savanna, Chaparral, Coniferous forests

Plant adaptations to fire

Above-ground survival (thick bark, tall trunks), below-ground survival (resprouting), generation from seed (seed dormancy, post-fire germination), flammability, serotonin (cones or seeds survive fire and open after fire)

Anthromes

Human-modified landscapes (>70% of land)

Biotic Homogenization

Increases in similarity of communities over time (caused by increased dispersal of common species, increased mortality of rare species, human selection of species, and urbanization)

Dispersal Corridors

Protected areas are connected by them to promote persistence of species metapopulation across patches

Translocation/assisted migration

Humans move genotypes of species to new locations, but its very time/money-intensive

Habitat Restoration

Humans manipulate abiotic/biotic conditions and promote desirable succession pathways

Values of biodiversity

Intrinsic Value: existence value (the species exists), intrinsic (other species have a right to exist)

Instrumental value: reaches human goals/desires (non-market consumption, exchange, amenity, scientific/educational)

Cultural value: bald eagle is a symbol for nation, bison as a part of native american cultures

Service value: shade, food impact reduction

Ecosystem services

Provisioning: products generated by nature

Regulating: improving life by cleaning air and preventing erosion

Cultural: contribution to knowledge and society

Supporting: maintenance of basic life processes

Protected Areas

Bigger area, more species

Economics on deciding nature protection

Economic frames nature by assigning money-based values instead of natural capital

Pros: gives common language for decision-making, could be more effective than community or government protests due to strength of market, comfortable framing for corporation and governments

Cons: assumes capitalism is all that matters, assumes buying/selling nature is ethical, neglects long-term effects but rather short-term changes in market, enables powerful and rich ppl to “pay to pollute”

The right framing of biodiversity

If humans have natural rights, then nature also has rights, not just a resource only used by humans, humans have responsibility to care for nature