Community and Ecosystem Ecology Flashcards

Community and Ecosystem Ecology

Ecology Definition

• Ecology is the study of the interactions between living things and their environment.

• It examines how organisms interact with each other and with the non-living components of their environment, such as air, water, and soil.

Levels of Biological Organization

The biological hierarchy extends from atoms to the biosphere:

• Atom (e.g., hydrogen)

• Molecule (e.g., water)

• Organelle (e.g., nucleus)

• Cell (e.g., neuron)

• Tissue (e.g., nervous tissue)

• Organ (e.g., brain)

• Organ System (e.g., nervous system)

• Organism (e.g., sea lion)

• Population (e.g., colony)

• Community (e.g., giant kelp forest)

• Ecosystem (e.g., Southern California coast)

• Biosphere (e.g., Earth)

Population Definition

• A population consists of individuals of the same species living in a given area.

Community Definition

• A community includes populations of different species living in the same place.

Ecosystem Definition

• An ecosystem is a community of living organisms interacting with the nonliving components of their environment (air, water, soil, etc.) as a system.

Ecology vs. Economy

• Both terms originate from the Greek word "oikos" (household).

• Ecology (oikos + logos = "study"): study of the household of nature, focusing on the flow of energy and matter.

• Economy (oikos + nomos = "to distribute, manage"): managing the household, concerning the "flow of wealth" (micro and macro economy).

Food Chains

• A food chain is a linear flow of energy and matter within an ecosystem.

  • Sun → producers → primary consumers → secondary consumers

• Producers: photosynthetic organisms.

• Primary consumers: feed on producers.

• Secondary consumers: predators that feed on primary consumers.

• Decomposers: feed on dead organisms and return minerals and carbon to the system.

• Energy flow is unidirectional (non-cyclic)

• Mineral nutrient movement and carbon flow are cyclic

Food Webs

• A food web is a natural interconnection of multiple food chains.

Trophic Levels and Pyramids

• The food chain can be organized into trophic levels, forming a trophic pyramid.

• A trophic level is each position on the food chain.

• The trophic pyramid represents the flow of energy and matter along a food chain.

• Approximately 10% of energy is transferred from one level to the next; about 1% of solar radiation energy is captured by plants.

Biodiversity and Extinction

• Biodiversity: variety of different types of life found on Earth.

• Extinction: the complete loss of a species.

• Extinction is a natural process, but it has dramatically increased in the last few hundred years.

• The current 10 million species represent only 1% of all species that have ever existed.

Current Extinction Crisis

• According to the World Conservation Union:

  • 42% of amphibians are in danger of extinction.

  • 26% of mammals are in danger of extinction.

  • 13% of birds are in danger of extinction.

  • 40% of conifers are in danger of extinction.

  • 23,000 species are endangered (governmental agencies and non-governmental organizations from 140 countries).

Mass Extinctions

• Mass extinctions involve species loss on a global scale, affecting large numbers of species and caused by massive global changes.

• Many scientists believe we are experiencing the beginning of the 6th mass extinction.

Primary Causes of Extinction (Human-Driven)

• Loss or degradation of habitat

• Introduction of non-native species

• Overexploitation of species

• Pollution

Habitat Loss and Degradation

• Loss or degradation of habitat is the most serious threat to biodiversity today.

• Habitat: the place where a particular species lives and obtains resources for survival.

• Habitat destruction involves the decline of natural landscapes, reducing the number of species supported.

  • It is caused by human use and development (agricultural, industrial, and residential) and affects all ecosystems.

• Habitat fragmentation: large natural areas are subdivided into smaller areas; especially threatening to large predators needing large hunting areas.

Introduction of Non-Native Species

• Non-native organisms, brought by human activity (either accidentally or purposely) to new environments, compete with native species for resources.

• Examples: zebra mussels, rabbits in Australia.

Overexploitation of Species

• Overexploitation occurs when the rate of human use of a species outpaces its reproduction.

Pollution

• Pollution is the release of poisons, excess nutrients, and/or other waste products into the environment.

• E.g., Eutrophication is the excess growth of photosynthetic bacteria that depletes oxygen from water, caused by excess fertilizer runoff, resulting in large fish kills.

Importance of Biodiversity

Consequences of Extinction

• Losing biodiversity means losing biological resources (currently used resources and potential resources).

  • Wood: fuel, lumber, paper.

  • Algae, Shellfish, Fish: food. About 100 million metric tons of aquatic life are taken from the wild every year.

  • Herbs: medicines, chemicals. Approximately 50,000-70,000 plant species are harvested for traditional and modern medicine worldwide (e.g., Rosy periwinkle, Foxglove).

  • Animals: meat, fur. Meat from wild animals forms a critical contribution to food sources in many countries.

  • Reservoir of genetic traits for domesticated plants and animals

• According to IUCN, the monetary value of goods and services provided by ecosystems is estimated to amount to > US33 trillion per year (roughly the yearly GDP of the US and European Union combined!).

• The impact to the economy of wild species in the United States has been calculated to be around 90 billion a year.

Ecological Consequences

• Extinction can lead to unpredictable direct/indirect outcomes. Different species occupy different ecological niches in the same habitat.

• Disruption in one strand affects other portions of the web.

Habitat vs. Niche

• Habitat: where an organism lives (e.g., a lake for trout).

• Niche: an organism's role in its environment.

• More habitats = More niches = more Biodiversity

Species Interactions

• What types of interactions do species establish?

• What are the effects of breaking those interactions?

Types of Interactions

1. Mutualism: interaction between two species that benefit each other.

   • Fungal mycorrhizae increase mineral absorption by plant roots and consume plant sugars.

   • Cleaner fish eat parasites from larger fish.

   • Thorns of acacia trees provide homes for ants, which defend the tree from other insects.

2. Commensalism: relationship in which one species benefits and the other is unaffected.

   • Egrets feed on insects stirred up by cattle (no benefit or harm to cattle).

   • Barnacles living on whales (no benefit or harm to whales).

3. Parasitism: relationship in which one species benefits (parasite) at the expense of the other (host), which is affected negatively.

   • Examples: Ascaris lumbricoides, ticks.

4. Predation: species that survives by eating another species.

5. Competition: occurs when two species require the same resources for life.

Case Study: Sparrow Extermination in China

• In 1958, Mao Zedong started a campaign to exterminate sparrows because “they ate grain seeds, robbing the people of the fruits of their labor.”

• The extermination of birds enabled crop-eating insects to proliferate.

• This ecological imbalance exacerbated the Great Chinese Famine, in which at least 20 million people died of starvation.

Keystone Species

• Keystone species play a key role in the food web of an ecosystem and have an unusually strong effect on the community.

• Removal of keystone species may cause the collapse of the web of life.

• Some predators can be keystone species.

Example: Wolves in Yellowstone

• Mid-1920s: Gray wolves were exterminated within Yellowstone Park.

• Aspen, cottonwood, and willow trees declined due to increased predation by elk.

• In the 1990s, wolves were reintroduced.

• Trees rebounded.

• Beneficial effects on beavers, warblers, insects, and fish that depend on shelter, food, and shade.

Competition and Human Effects

• Antibiotics to treat bacterial infections also kill beneficial bacteria (human microbiome), leading to yeast infections.

• Mosquitoes, snails, and tadpoles compete for algal resources in ponds.

• Mosquitoes increase when populations of snails and tadpoles decrease.

• Mosquitoes may carry malaria, West Nile virus, yellow fever, Zika.

Genetic Resources

• Biodiversity serves as a reservoir of genetic traits for domesticated plants and animals.

• Example: Teosinte

Factors Affecting Population Size

• Population size = Birth rate - Death rate

• Resources and competition for these resources among members of the population

• Interactions with other species

History of Biodiversity

Mass Extinctions

• Mass extinctions are species losses that are global in scale (affect large number of species and are dramatic in impact), likely due to big climate fluctuations, change in sea levels, asteroid impact…

Sixth Mass Extinction

• Many scientists argue that we might be undergoing a 6th mass extinction due to human activity.

Trophic Pyramid

• Trophic pyramid: the flow of energy and matter along a food chain.

• Most biomass (matter) at bottom level.

• Much energy lost as heat between levels.

Current Extinction Rates

• Extinction has dramatically increased in the last few hundred years.

• Is this a Man-induced process?

Background Extinction Rate

• Background extinction rate: the rate at which species are lost through the normal evolutionary process.

• Extinction occurs when:

  • Species lack variability to adapt to the environment.

  • New species arise due to evolution.

• Extinction is a Natural Process.

Measuring Extinction

• Current extinction rate: calculated from known species disappearances.

• Challenging to calculate.

• Standard for extinct status: no individuals of a species are seen in the wild for 50 years.

• More than three times as many species of birds and mammals have gone extinct in the last 150 years than had in the previous 250 years.

Species-Area Curve

*Species-area curve: measures the relationship between the size of natural areas and the number of species supported.

*How can we calculate the impact that habitat loss/degradation has on species extinction?
*Basically, the less habitat space available, the lower number of species

Predicting Extinction

*Species area curve: used to predict extinction caused by habitat destruction.

*Estimates rates of extinction in regions rapidly changing due to human activity
*At present rate of global habitat destruction, 25\% of all species could become extinct within 50 years.

Pollution and Extinction

• Pollution: the release of poisons, excess nutrients, and other waste products into the environment.

  • e.g.: Carbon dioxide: most abundant atmospheric pollutant, associated with climate change.

  • 15 – 37% of plants face extinction due to global climate change.

Mutualism: Bees and Flowering Plants

• Bees collect excess pollen and nectar for food. In doing so, they pollinate flowers.

• Wild bees pollinate 80\% of agricultural crops in the United States (Economic benefit of 8 billion).

• Currently, there is a decline in bee populations due to “colony collapse disorder”.

Predation: Songbirds and Forests

• Wood warblers voraciously consume insects.

• Most insects eaten by warblers prey on plants.

  • Reduces insect damage to forest plants.

  • Increased tree growth.

  • 200 billion in paper and lumber products in the United States.

• As songbird numbers decline, damage to forests increases.