Chapter 4Ecosystems

Standard 2: Students know and understand the characteristics and structure of living things, the processes

of life, and how living things interact with each other and their environment.

Concepts and Skills to Master:– Matter tends to be cycled within an ecosystem,

while energy is transformed and eventually exits an ecosystem.

Vocabulary

Abiotic factor algal bloom Biomass biotic factor Carnivore commensalism Ecosystem estivation Food web herbivore Humus niche Omnivore trophic level Pyramid of biomass pyramid of energy Pyramid of numbers First-order consumers Video: approx. 60 min Second-order consumers Third-order consumers

Organisms and their Environment (20:00)

Interactions Among Organisms

In every community, organisms interact with one another. The relationships between the different organisms is known as the biotic factor in an environment.

Biotic Factor is the relationship between living things (3:57)

The interaction of a community with its environment is an ecological system also called an ecosystem.

In almost all ecosystems, the original source of energy starts with the sun.

Succession

Due to changes in an ecosystem like volcanoes, floods or drought opportunities arise for different organisms to replace existing ones in a single place over time in a process called succession.

First where there was bare ground, pioneer species will grow, then be replaced by grasses and shrubs, then eventually trees.

Succession

Major Biomes

A biome is a large region characterized by a specific kind of climate and certain kinds of plant and animal communities.

Climate is the average weather conditions over a long period of time in a specific area.

Two key factors that determine the types of biomes that exist are temperature and precipitation.

Terrestrial Biomes

Major terrestrial biomes can be grouped by latitude into:

Tropical (at the equator) Temperate (Mid latitudes) High Latitude (Cold temperatures)

Aquatic Ecosystems

Freshwater (bodies of fresh water—rivers, lakes ponds)

Wetlands (link between land and fully aquatic habitats)

Estuaries (where river and ocean meet) Marine (fully aquatic, salty waters of the

oceans)ss Virtual Investigation (DVD) on Ecosystems

and Energy pyramids.

World Biomes (25:49)

followed by quiz # one

The flow of energy (2:05)

Interactions between organisms involve the exchange of energy, usually by feeding upon one another. Thus, each organism represents a feeding step called a trophic level.

Marine trophic level

Niche

A niche describes how an organism fits into an ecosystem.

Because each organism is unique, no two organisms can occupy the same niche in an ecosystem. Niches (1:33)

Trophic levels (1:33)

Producer (plants, Autotrophs or Photoautotrophs)

First-order consumers (herbivores)

Second-order consumer (carnivores)

Third-order consumer (large carnivores)

Decomposers are consumers as well.

Omnivores eat both plants and animals.

Food Chains (1:53)

Which is which?

Decomposers (0:54)

When any organism dies, it is eventually eaten by detrivores (like vultures, worms and crabs) and broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues.

Food Web All the possible

feeding relationships that exist in an ecosystem make up a food web.

What are the primary producers, 1st, 2nd and 3rd consumers in this marine food web?

Construct food web

Marine Food Web (2:10)

Pyramid of Energy (1:05)

The transfer of energy within an ecosystem is called the pyramid of energy.

Energy originally produced is not lost, just changed into different forms of energy such as heat.

Energy can also be stored—more than ½ of the potential energy in each food molecule is lost as heat energy during cellular respiration.

Pyramid of numbers (1:55)

The loss of energy between the trophic levels explains why there are fewer organisms in each higher level than the previous one.

This relationship is called the pyramid of numbers.

The pyramid of numbers does not apply to all food chains. An exception would be where a large organism is fed upon by smaller ones. Example: a dog infested with parasites.

Biomass (1:24)

Biomass is the amount of dried organic matter at different trophic levels.

Most ecosystems have a pyramid of biomass.

Aquatic systems do not form a pyramid because most of the producers are microscopic algae.

Commensalism

Commensalism occurs when one organism benefits from another without aiding or harming the host.

Remoras are “hitchhiker” fish that eat the leftovers of larger fish. They don’t help or hurt the fish, so it’s a commensal relationship.

Whaleshark and remora

Carbon Cycle in an Ecosystem

Energy is not cycled but replaced by sunlight’s energy.

Carbon dioxide from aerobic respiration, fuel emissions and volcanic activity is recycled into organic and inorganic substances.

Click for Carbon Cycle (11:07)

Mutualism

Mutualism is a mutually beneficial relationship between organisms.

The bee feeds on the flower and pollinates it at the same time. Both benefit.

Coral Reef Ecosystem (3:49)

Bee and flower

Parasitism

A parasite is an organism who is dependent upon a host.

Indian paintbrush (Castilleja indivisa) is a parasitic plant that obtains some of its nutrients and water from host plant--bluebonnet (Lupinus texensis).

Indian paintbrush and bluebonnet

Abiotic Factors of the Environment

Physical aspects of an ecosystem affect the reproduction, feeding, growth and metabolism of organisms within that system.

Abiotic factors include:– Water– Soil– Light– Temperature Abiotic Factors are

the relationship between non-living things.

All organisms need water.

Available water is a limiting factor for organisms.

Evaporation, condensation and precipitation are the primary phases in the water cycle.

Water cycle (click here)

Soil

Soil is important to organisms because it’s where plants grow and animals make their homes.

Soil holds many microorganisms and decomposers that are important for the cycling of materials.

Humus is the decayed remains of organisms in soil.Soil layers

Let there be Light

Light is the source of energy for almost all ecosystems. It provides the energy for photosynthesis:

6CO2 + 6H2 O C6H12O6 + 6O2

Light is also required for vision, and heat absorption that results in evaporation.

Temperature Organisms are

adapted to survive within particular temperature ranges.

Temperatures change from day to night and season to season.

Temperature and day length can cause mammals to migrate or hibernate in winter.

Metabolic rate decreases during hibernation.

Hazel dormouse hibernating in burrow

Temperature can also affect metabolic rate (activity of enzymes). Organisms cannot survive above 50oC because enzymes are destroyed.

Lizards compensate for desert heat by shading up during the day while some frogs go dormant.

Summer dormancy is called estivation.

Sand diving lizard

Disrupting the Balance An ecosystem can be

temporarily altered by biotic and abiotic factors.

Both these factors help regulate population sizes in that resources are not overused.

Naturally occurring disruptions include floods, earthquakes and volcanoes.

Human Activities and Nature’s Balance

(1:33) Certain human activities can alter nature’s delicate balance.

Too many phosphates from detergents can increase algae, creating an algal bloom that eventually suffocates other organisms.