Chapter 3-7: Ecology

Studying Our Living Planet

Ecology: study of the interactions between organisms and nonliving components of their environment

• Broad science (includes organisms and their environments)

• Measuring and observing interactions

• Observing patterns

Interdependence: relationship on how different species rely on each other and on the nonliving components of their environment

• Survival depends on interactions

• Any changes in the environment spreads through interactions

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Biosphere: consists of all life on Earth and all parts of Earth in which life exists including land, water, and atmosphere

• Broadest level of organization

Biome: a group of ecosystems that share similar climates and organisms

• Examples

  • Rainforests

  • Desserts

  • Grasslands

Ecosystem: all of the organisms and the nonliving environments in a particular place

• Examples

  • Pond, lake, ocean

  • Garden, field

Community: all of the living organisms in an area

• (different populations of individuals)

Population: a group of individuals that belong to the same species and live in the same area

Species: a group of related organisms that are capable of producing fertile offspring

• Example

  • Mules ARE NOT a species because they are not fertile

Organism: individual living thing

Biotic and Abiotic Factors

Environment: All conditions or factors surrounding an organism

Biotic factors: any living or once-living parts of the environment with which an organism might interact

Abiotic factors: any nonliving part of an environment

• Physical and Chemical characteristics

Habitat and Niche

Habitat: an area with a particular combination of physical and biological environments facts that affect which organisms can within it

• The actual place an organism lives

• Silimar habits can exist in many parts of the world

Niche: range of physical and biological conditions in which a species lives and the way the species obtains what it needs to survive and reproduce

• Physical use of habitat

• Tolerable conditions

• Resources available

• Niches may overlap

Range of tolerance: variety of environmental conditions within which a species can survive and reproduce

• Within the optimum range, organisms can thrive

• Conditions that fall outside of range cause stress

  • Difficulty maintaining homeostasis

  • Produce fewer offspring

  • Fewer offspring survive

  • Extreme stress causes death

Population Growth

Populations increase, decrease, or stay the same depending on how many individuals are added or removed.

Immigration: individuals that move into a population from elsewhere

Emigration: individuals that move out of a population

Populations increase in size when birthrates and immigration are higher than death rates and emigration

Populations decrease in size when birth and immigration are lower than death rates and emigration

Populations do not change in size when birthrates and immigration are equal to death rates and emigration

Exponential growth: under ideal conditions with unlimited resources, a population will increase exponentially

• The larger the population, the faster it grows

• Cannot be sustained indefinitely

Logistic growth: The population’s growth slows and then stops following a period of exponential growth

Limiting factors: any factor that contributes to the control of population growth

• Examples

  • Competition

  • Disease

  • Space

  • Nutrients

Carrying Capacity: max number of individuals of a particular species inin a specificnvironment

Energy

All living things require energy

• Expend energy for metabolic processes

• Growth, movement, development, reproduction, maintenance, repair, etc.

All organisms need to obtain energy from the environment

Different types of organisms obtain energy in different ways

Primary producers: organisms that capture energy and use it to make organic molecules

• Examples

  • Plants

  • Bacteria

  • Some Protist (Algae)

• Photosynthesis: producers that use energy from the sun and CO2 to power cell activities

• Chemosynthesis: chemical energy is used to produce carbs to power cell activities

Consumers: organisms that gain energy by consuming other organisms or waste

• Carnivores: obtain energy by killing and consuming other animals

• Herbivores: organisms that only eat producers

• Omnivores: eat both plants and animals

• Scavengers: consume carcasses (dead bodies) of other animals

• Decomposers: “feed“ by chemically breaking down organic matter

  • Examples

    • fungus

    • bacteria

• Detritivores: chemicals that feed on detrias particles, waste, dead organisms

  • Examples

    • Worms

    • Mites

Categorizing consumers does not express the complexity of nature

Some animals move between categories

• Examples

  • Hyenas—Carnivores, but will savenge

Trophic levels: feeding relationships in an ecosystem

• Indicate an organism’s position in the sequence of energy transfers

• Can be fluid

1. Tertiary Consumers ←HIGHEST (LAST)

2. Secondary Consumers

3. Primary Consumers

4. Producers

5. Light/Chemical Energy ←LOWEST (FIRST)

Ecological pyramids: shows the relative amount of energy contained in each tropic level

• Energy stored in tissues of organisms

The efficiency of energy transfer varies — no limit to the amount of trophic levels

On Average 10% of the energy available within a trophic level is transferred to the next level

The more levels that exist between a producer and a consumer, the smaller the percentage of energy available

Food Chains and Food Webs

Food chain: series of steps in which organisms transfer organisms transfer energy

• varies in length depending on organisms in ecosystems

Food web: a network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem

• Outlines more feeding relationships

• More inclusive

Feeding relationships are delicate

Environmental changes can disrupt entire feeding patterns, and therefore entire ecosystems

• Weather

• Pollution

• Disease

• Extinctions

• Immigration/Emigration

• Overharvesting

• Habitat destruction

Species Interactions

Communities contain interacting populations of many species

Types of interactions:

• Competition: when two organisms attempt to use the same essential resource, which can’t be shared

  • Can occur between members of the same or different species

  • Direct completion always produces a winner and a loser

  • Interspecific competition: competition between individuals of different species

  • Intraspecific competition: competition between individuals of the same species

• Predation: an interaction in which one animal (pred) eat all or part of another animal (prey)

  • Relationship influences population size

  • Determine places pred and prey can live

• Herbvivory: an interaction in which one animal (herbivore) feeds on producers (plants)

  • Relationship influences the size and distribution of plant populations

• Keystone species: a species that plays a vital and unique role in maintaining structure, stability, and diversity in an ecosystem

• Symbiosis: a close independent relationship between two species

  • Mutualism: the relationship between two species where both benefit from each other

    • Some organisms cannot live without each other

      • Honeybees and flowers

  • Parasitism: relationship in which one organism (parasite) lives on or inside another organism (host) and harms it

    • Parasites obtain all nutritional needs from the host

    • Weaken but do not kill the host immediately

    • The host is usually larger than a parasite

    • Examples

      • Tapeworms

      • Ticks

      • Fleas

      • Lice

  • Commensalism: a relationship in which one organism benefits and the other is neither harmed nor helped

    • Example

      • Cape buffalo and egrets

Recycling in the Atmosphere

Matter also moves through the biosphere

Matter is recycled within and between ecosystems

Biochemical cycles: process by which elements, chemical compounds, and other forms of matter are passed from one organism to another and /or from one part of the biosphere to another

• Biological processes:

  • Any and all activities performed by living organisms

    • Eating, breathing, eliminating waste, etc.

• Geological processes:

  • Volcanic eruptions, formations and breakdown of rock, major movements of matter within and below Earth’s surface, etc.

• Chemical and physical processes:

  • Formations of clouds, precipitation, etc.

• Human activities:

  • Mining and burning fossil fuels, clearing of land, building, farming, burning of forests, manufacturing, etc.

The Water Cycle

Water continuously moves between oceans, atmosphere, and land

Involves evaporation (liquid → gas) and condensation (gas → liquid)

Nutrient Cycles

Nutrients: chemical substances that an organism needs to sustain life

Three main cycles critical to life:

1. The Carbon Cycle

   • Major component of all organic compounds

     • Essential to form carbs, proteins, lipids, and nucleic acids

   • Continuously cycled through land, eater and atmosphere

   • Some C containing compounds from ancient times

   • Involves humans, animals, and plants

   • Human activity contributes to the amount of C

2. The Nitrogen Cycle

   • Required by all organisms to make proteins and nucleic acids

   • Continuously cycled through atmosphere, water and land

   • Human activity contributes to the amount of N

   • Nitrogen fixation: conversion of N gas to ammonia (NH3) by bacteria

   • Denitrification: conversion of nitrates (NO3) and nitrites (NO2) into N gas by bacteria

3. The Phosphorous Cycle

   • Essential for nucleic acid formation

   • Continuously cycled through land and water

   • Mainly stored in rock formations

   • Human activity contributes to amount of P

Nutrient availability relates to the productivity of an ecosystem

Primary productivity: rate at which primary producers create organic material

Limiting nutrient: the nutrient whose supply limits productivity

• If any given nutrient is limited, ecosystem productivity decreases

Ecosystem Services and Biodiversity

Humans depend on healthy ecosystems

Ecosystem services: benefits provided by ecosystems to humans

1. Food Production

   • Healthy ecosystems provide an abundance of food

2. Nutrient cycling and soil structure

   • Cycling of nutrients keep soil healthy

     • Keeps plants healthier

       • Better food for animals/humans

3. Water purification

   • Freshwater is filtered and purified through the ground and microorganisms

4. Storing carbon

   • CO2 is removed and stored as C in healthy marine and terrestrial ecosystems

5. Regulation of pests

   • Healthy pred/prey relationship keeps pests and therefore disease and destruction down

6. Buffer for extreme weather

   • Healthy ecosystems protect against erosion, landslides, runoff, etc.