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Survey of Ecology What is Ecology?

• Ecology is the scientific study of the interactions between organisms and their environment.

• Natural History and Beyond• Two critical parts:

– Organisms– Environment

Interdisciplinary science Organism distribution and abundance

• Interactions between organisms and their environment determine their distributions and abundance– Distribution

• Geographic range of an organism

– Abundance• Degree of plentifulness

Distribution and abundance What makes up the environment?• Biotic and Abiotic components

– Biotic• All Living components

– Abiotic• All the non-living chemical and physical factors

that affect living things

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Weather and Climate on living scales

• Microclimates– Local Scales

• Rain Shadows, • Coastal Effects,

Lake stratification

– Very small scales

World Biomes

Land-linked Aquatic Biomes

• Lakes• Rivers• Streams• Wetlands• Estuaries

Ocean Biomes

Characteristics of Populations

•• What is a Population?What is a Population?–– A group of individuals of a species that A group of individuals of a species that

occupy the same areaoccupy the same area•• Two parts: Two parts:

–– 1) need to be same species1) need to be same species–– 2) spatial delineation2) spatial delineation

–– So, what are So, what are individualsindividuals? Do you know ? Do you know them when you see them?them when you see them?

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Rates of Growth• Some examples…

‘Of rice and men’

Lets graph it…

9,223,372,036,854,780,000 Logistic Growth

• Real world growth is usually not exponential…for long.

• Limited resources put many pressures on growing populations

• Carrying capacity– “K”

• Maximum population size that a particular environment can support at a particular time, with no harm to the habitat.

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Carrying capacity and growth rates K and r selection• At high population densities (close to ‘K’)

– Selection favors adaptations that help organisms survive and reproduce with few resources

– Efficiency and Competition• At low population densities

– Selection favors rapid reproduction and shorter lifespans

• K-selection- density dependent• r-selection- density independent

dN/dt=r [(K-N)/K]

Competition review

• Ecological Niche– Sum total of a species’ use of the biotic and

abiotic resources in its environment– How a species “fits” into an ecosystem– Competitive Exclusion Principle- Exclusion if

two species share the same niche– Only need to have one difference in a niche to

get a foothold

All these act on the individual, but are measured at the population

Competition cont.• Resource Partitioning

– Two outcomes of competition: extinction of one, or evolve to a different niche

– Character Displacement

Character displacement

• “The ghost of competition past”- Connell, 1980

Community Ecology• Community: all species which interact in the same area;

an assemblage of populations– What factors are most important in structuring a

community?– What factors determine the composition of species?– What factors determine the abundance of each species?

• Communities vary by their:– Composition or Species Richness– Relative Abundance– Biodiversity

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Interspecies Interactions

• Species interaction, of many different types, can help structure communities– Competition– Predation– Symbiosis

Competition

• Interspecific competition– Competition can result in lower density of one

or both species• Competitive Exclusion Principle (CEP)

– One species that has even a slight advantage will exclude others.

Competition in the Intertidal

High Tide

Low Tide

Realized Niches

Fundamental Niches

Zone of Competition

J. Connell, 1961

Predation• Many types of predation

– Herbivore, parasite, carnivore, – A powerful factor in natural selection

• Predator adaptation-– Many familiar adaptations for feeding– Defensive adaptations- Plant and animal

Plant defensive adaptations• Plants

– Cant run away, so have evolved a large number of anti-herbivore strategies

• Chemical toxins – “MAY BE FATAL IF ABSORBED THROUGH SKIN/ INHALED/INGESTED.

EXPOSURE CAN CAUSE LIVER & KIDNEY DAMAGE/ADVERSE REPRODUCTIVE EFFECTS/DELAYED LUNG INJURY/CARDIOVASCULAR SYSTEM INJURY/ RESPIRATORY TRACT IRRITATION/DELAYED ADVERSE HEALTH EFFECTS/NERVOUS SYSTEM INJURY. POSSIBLE CUMULATIVE POISON.”

• Spines/thorns• Thick epidermis

Animal defensive adaptations

• A number of ways to avoid being eaten• Run away!!, hide, defend, alarm, gang up,

school– Cryptic coloration– Transparency

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• Aposematic coloration– Warning coloration

Animal defensive adaptations Trophic Structure

• Feeding relationships- Who is eating whom• The transfer of energy through the

community• Chains and webs

Food webs What limits the number of chains?

• Why typically have only 4-5 trophic levels?– The 10% rule– On average, only about

10% of the energy taken in by one link is passed on to the next.

Biodiversity

• Biodiversity-– Species richness– Relative

abundance• How put these

together?• Indexes of

Diversity– Shannon Index– Simpson’s Index

Ecosystems

• All organisms living in a given area with the abiotic factors with which they interact

• Not discrete areas• The most inclusive of biological

organization• At the ecosystem level we often study the

flow of energy and nutrients in the system

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Primary production• Each day 100 million atomic bombs worth of solar

radiation strikes the earth• Only a small fraction used for photosynthesis• Gross Primary Productivity

– Total production per unit time; not all stored, some used for immediate respiration

• Net Primary Productivity– Gross Primary Productivity- respiration

• Light/Dark Bottles

– True unit of interest

Primary production- biomass

Conservation Biology• Goal-oriented science that seeks to counter the

current rapid decrease in biodiversity• The Biodiversity crisis- human activities alter

ecosystem processes, alter landscape and trigger extinctions

Three Levels of biodiversity

• Genetic diversity• Species diversity• Habitat / community

diversity

Three Levels of biodiversity

1. Genetic diversity– Variation within and between

populations– Genetic diversity allows for

adaptation to changing conditions– If populations loose genetic

diversity they loose adaptive ability– Once genetic diversity is lost it

takes evolutionary time to get it back

Three Levels of biodiversity2. Species diversity

– Loss of species richness– 13% of 9,040 bird species threatened– 47% of all plants worldwide may be

threatened– 20% of freshwater fish extinct of

threatened– Since 1900, 123 extinct freshwater

vert and inverts in North America– Many animals are in the Hundred

Heartbeats club

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Three Levels of biodiversity

3. Habitat / community diversity

– Extinction of on species could have negative impact on others in the system

– Each system can have an important impact on the whole biosphere

Benefits of diversity• Biophilia- innate connection to nature and life• Anthrocentric

– Species are a natural resource for food, fibers, medicines, etc.

– Do all species have an innate value? Are some worth more than others? Who decides?

– Ecosystem services• Often overlooked benefits to humans:

Air, water, soil, detoxification, decomposition, pollination, seed dispersal, nutrient cycling, protection from UV, moderation of weather…aesthetic beauty and infinite source of wonder

• Estimated at $33 trillion/year (1997)- 2x global GNP

– Other studies estimate at only5-10 trillion dollars

Four major threats to biodiversity

1. Habitat destruction2. Introduced species3. Overexploitation4. Disruption of food chains

Four major threats to biodiversity1. Habitat destruction

• Single greatest threat to biodiversity• Over 70% of extinct, endangered, threatened species

from loss of habitat• 93% of reefs are damaged- 1/3 of fish species are in

coral reefs which make up only 0.2% of ocean.• Large variety of human uses impact habitat loss

• Living, food, recreation, materials, fuels, etc…

• Landscape fragmentation• Habitat size is not the only issue, contiguous pieces are also

important

Habitat fragmentation Four major threats to biodiversity2. Introduced species

• Second biggest problem- linked to 40% of extinctions• “Exotic species”- species humans have moved from

one location to another, sometime intentionally, sometimes not

• Successful exotics often disrupt their new community, prey on and/or compete with native species

• 50, 000 in U.S. alone, damage control = $130 billion• Some examples…

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Carcinus maenas- Green Crab

• First collected on west coast in S.F.- 1989 • Moved to Bodega Bay by 1993• Found in Monterey by 1994

Four major threats to biodiversity3. Overexploitation

– Human harvesting of plants and animals exceeds ability of populations to rebound

– Species especially susceptible are those with low reproductive rates

– The “inexhaustible seas”

MBA Seafood watchhttp://www.mbayaq.org/cr/seafoodwatch.asp

Four major threats to biodiversity4. Disruption of food chains

• Loss of one species in an ecosystem can have negative impacts on there species

• Remove the prey, the predators will suffer• Loss of Keystone species…• Since most organism do not depend on just a single

prey species, this can be a very difficult thing to quantify

Restoration Ecology• Restoration ecology is the study of recuperating degraded,

damaged or destroyed ecosystems through active human intervention– current extinction rate are 1000 to 10,000 times the

‘normal’ rate (E.O. Wilson 1988)• The fundamental difference between conservation biology

and restoration ecology lies in their philosophical approaches to the same problem:– Conservation biology attempts to preserve and maintain

existing habitat and biodiversity. – In contrast, Restoration ecology assumes that

environmental degradation and population declines are somewhat reversible processes. Therefore, targeted human intervention can lead to habitat and biodiversity recovery and eventual gains

• restore a natural disturbance • hastening natural successional

trajectories • increase the effective size of a habitat by

simply adding area or by planting habitat corridors that link two isolated fragments

• monitoring and management are crucial for the long-term stability

• working toward a single desired stable state

The goal of restoration is not to immediately recreate replacement ecosystems, rather to “jump-start” natural recuperative processes.

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How can we be part of the solution?

• It is depressing stuff, but an informed public can be a very powerful thing

• U.S. ranks at the top of most graphs, so we can have a disproportionate positive effect

• What can you do?– Stick your head in the sand– Other options…

Environmental Issues• Human impacts on

nutrient cycling• Combustion

byproducts• Increasing levels of

CO2

• Pesticide and fertilizer issues

• Loss of Ozone• Loss of biodiversity• Habitat loss• Overexploitation• Introduced species

What can you do to make a difference?

Shameless Plug:

Biol 31-Environmental Science

Bio 32- Enviro Sci lab.