Introduction to Ecology: Ecosystems, Energy Flow, and Biodiversity

abiotic

Non-living chemical and physical parts of the environment that affect living organisms.

adaptation

A trait that helps an organism survive and reproduce in its environment.

assimilation

The process by which organisms incorporate nutrients from their environment into their own body.

biodiversity

The variety of life in the world or in a particular habitat or ecosystem.

biomass

The total mass of organisms in a given area or volume.

biotic

Living components of an ecosystem.

chemosynthesis

The process by which certain organisms create energy by using chemicals, rather than sunlight.

commensalism

A type of symbiotic relationship where one organism benefits and the other is neither helped nor harmed.

community

All the populations of different species that live in one place at one time.

consumers

Organisms that obtain energy by feeding on other organisms.

decomposers

Organisms that break down dead or decaying organisms, returning nutrients to the environment.

detritivore

An organism that feeds on dead organic material, especially plant detritus.

exponential growth

A growth pattern in which the population size increases at a constant rate over time.

generalist species

Species that can thrive in a wide variety of environmental conditions and can make use of a variety of resources.

geographic isolation

A form of reproductive isolation in which two populations are separated by geographic barriers.

greenhouse effect

The warming of the Earth's surface due to the trapping of heat by greenhouse gases.

indicator species

Species that provide a sign of the quality of the ecosystem's environmental conditions.

invasive species

Non-native species that spread widely in a new habitat and can cause harm to the environment.

K-selected species

Species that produce fewer offspring but invest more resources in raising them.

keystone species

A species that has a disproportionately large effect on its environment relative to its abundance.

logistical growth

A growth pattern that starts with a period of exponential growth followed by a leveling off as resources become limited.

mutualism

A type of symbiotic relationship where both organisms benefit.

population

A group of individuals of the same species that live in the same place at the same time.

primary productivity

The rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances.

primary succession

The process of community development on a site that has never supported life before.

producers

Organisms that produce their own food, typically through photosynthesis.

r-selected species

Species that produce many offspring but invest little in their upbringing.

scavengers

Organisms that consume dead animals.

secondary succession

The process of community development on a site that has previously supported life but has been disturbed.

specialist species

Species that have a narrow ecological niche and specific habitat requirements.

transpiration

The process by which water is absorbed by plant roots and then evaporated into the atmosphere from plant surfaces.

trophic level

The position an organism occupies in a food chain.

natural selection

The process by which organisms better adapted to their environment tend to survive and produce more offspring.

One-way flow of energy

Energy from the sun arrives at the earth in the form of solar radiation, which is required for life on earth.

Solar radiation

Approximately half of solar radiation is in the form of visible light, 40% as infrared radiation, and less than 10% as ultraviolet radiation.

Primary producers

Only about 0.1% of all solar energy is captured by primary producers to start the food web.

First and second laws of thermodynamics

As solar radiation is utilized, low-quality heat is released into the environment.

Cycling of nutrients

The earth acts as a closed system for matter, requiring a fixed supply of nutrients to be recycled to support life.

Force of gravity

Gravity holds our atmosphere close to earth and facilitates the flow of nutrients and water, vital for the growth and reproduction of organisms.

Atmosphere

The majority of the atmospheric mass exists within the first two layers extending up from the earth's surface.

Troposphere

The bottom layer of the atmosphere where weather occurs, extending anywhere from 0-17 km above the earth's surface.

Composition of troposphere

The troposphere is 78% nitrogen, 21% oxygen, and 1% includes mostly argon gas and greenhouse gases.

Greenhouse gases

Naturally emitted gases including water vapor, carbon dioxide, and methane that warm the earth's surface.

Stratosphere

The layer of the atmosphere that contains the ozone (O3) layer, filtering out approximately 95% of harmful incoming ultraviolet light.

Hydrosphere

Consists of all of the water available on the planet, found in forms such as liquid, ice, and water vapor.

Erosive forces

Water is a powerful force that continuously shapes our earth through erosive processes.

Oceans coverage

About 71% of the surface of the earth is covered by oceans.

Biosphere

The earth has four major systems that regulate and support life: atmosphere, hydrosphere, geosphere, and biosphere.

Lithosphere

Comprises the crust and the top of the upper mantle.

Upper mantle

The layer of the earth located beneath the lithosphere.

Asthenosphere

The layer of the earth located beneath the upper mantle.

Lower mantle

The layer of the earth located beneath the asthenosphere.

Crust

The outermost layer of the earth, consisting of soil and rock.

Water vapor

A form of water found in the hydrosphere.

Geosphere

The geosphere consists of the earth's crust, mantle, and core.

Natural Capital

The earth's crust and mantle contain the soil and rock system that house the nonrenewable fossil fuels and minerals we use as natural capital.

Nutrients in Soil

The soil contains valuable nutrients, such as nitrates and phosphates, which support living organisms.

Depth of Biosphere

The biosphere extends from the depths of the oceanic floor where hydrothermal vent communities thrive to approximately 9 km above the surface of the earth.

Biomes

Scientists have divided major terrestrial life zones into biomes that have distinct climates that dictate their unique flora and fauna.

Aquatic Life Zones

Aquatic life zones have been divided into two major zones: marine zones and freshwater zones.

Marine Zones

Marine zones include salt water areas, such as intertidal, coral reefs, open-ocean, and estuarine areas.

Freshwater Zones

Freshwater zones include lakes, rivers, and streams.

Ecosystem Structure

Earth's life zones have been organized into biomes based on the abiotic (nonliving) and biotic (living) factors that exist in that region.

Abiotic Factors

Abiotic factors such as nutrients, temperature, solar energy, and water can predict what type of flora and fauna will be successful in that area.

Range of Tolerance

Each organism can live only within a specific range of tolerance for the physical and chemical variations that exist within their environment.

Optimum Range

Most species will have an optimum range at which their growth will be maximized.

Limiting Factors

Certain abiotic factors will limit a population's ability for growth and reproduction.

Nutrients for Plant Growth

Nitrates and phosphates, necessary nutrients for plant growth and development, are often in limited supply in the soil.

Energy Flow in Ecosystems

Organisms in the ecosystem are organized into a hierarchy of feeding orders or trophic levels.

Trophic Levels

Trophic levels are assigned based on the organism's method for acquiring energy and nutrients from the ecosystem.

Photosynthesis

Photosynthesis is the process where solar energy is converted into energy-rich carbohydrates for consumers.

Photosynthesis Equation

Photosynthesis: Solar energy + 6H2O + 6CO₂ → C6H12O6(glucose) + 602.

Dominant Producers

On land, the dominant producers are green plants.

Phytoplankton

Single-celled algae that float on the surface of the ocean and are important global primary producers.

Hydrothermal vent communities

Communities found deep on the oceanic floor that thrive without sunlight, relying on specialized bacteria as producers.

Bacterial chemosynthesis reaction

Heat + 3H2S + 6CO₂ + 6H₂O → C6H12O6 (glucose) + 3H2SO4.

Heterotrophs

Another term for consumers, meaning 'other-feeders' that obtain energy by feeding on other organisms.

Aerobic respiration

The process by which consumers break down glucose with the use of oxygen, releasing carbon dioxide.

Aerobic respiration reaction

C6H12O6 + 6O₂ → 6CO₂ + 6H₂O + energy.

Anaerobic respiration

The process by which decomposers break down organic compounds without the use of oxygen.

Ethanol fermentation

C6H12O6 (glucose) → 2C₂H₅OH (ethanol) + 2CO₂.

Primary consumers

Herbivores that eat only primary producers, such as rabbits, deer, some insects, and zooplankton.

Secondary consumers

Carnivores and omnivores that feed on other consumers for energy.

Carnivores

Consumers that rely only on feeding on other heterotrophs.

Omnivores

Consumers that feed on both other consumers and plants.

Tertiary consumers

Predators at the top of the food chain, typically carnivores with few natural predators.

Detritivores

Consumers that feed on detritus material, which is composed of dead organisms and waste fragments.

Decomposition

The process by which decomposers recycle organic material from dead organisms into inorganic nutrients.

Enzymes

Substances secreted by decomposers to help break down the body tissue of organisms.

Food Chain

A food chain simply shows the movement of energy from one trophic level to the next.

Food Web

A food web shows the more complex interrelationships of energy flow from one organism to another that exists in a diverse community.

Ecological Efficiency

The ecological efficiency in an ecosystem refers to the percent of usable chemical energy that is transferred as biomass from one trophic level to the next.

Second Law of Thermodynamics

According to the second law of thermodynamics, most of this energy is lost as heat as it moves from one level to the next.

Energy Loss in Trophic Levels

In general, 90% of the usable energy is lost as heat to the environment, and the organism in the next trophic level only gains (on average) 10% of the energy from the available biomass in the supporting trophic level below.

Trophic Level Energy Example

If 10,000 kcal are available at the first trophic level (primary producers), only 1,000 kcal would be available to the primary consumers, 100 kcal would be available to the secondary consumers, and only 10 kcal would be available to the tertiary consumers.

Gross Primary Productivity

Gross primary productivity is defined as the rate at which primary producers convert solar energy into chemical energy through photosynthesis.

Net Primary Productivity

Net Primary Productivity = Gross Primary Productivity (photosynthesis) - aerobic respiration (by plants).

Effect of Latitude on Productivity

As you move away from the equator, primary productivity will decrease.

Biodiversity and Energy

Biodiversity will also decrease due to the lack of available energy needed to support the various populations in the community.

First Trophic Level

Producers (plants).