Ecology Notes

Abiotic and Biotic Factors---

1.      ecology---study of interactions that occur among organisms and their environment

2.      abiotic--- nonliving physical factors that affect organisms living in a particular area

1. atmosphere, water, soil, temperature
2. sunlight—the source of energy for life on Earth
3. climate—an area’s average weather conditions over time

3.      biotic---living or once-living parts of the environment (plants, animals, bacteria, decaying matter)

3.  six levels of environmental organization---

1. organism or individual: a single living thing; one individual of a species (one deer)
2. population: all the members of the same species living together in an ecosystem (all of the deer)
3. community: groups of populations that interact with each other in an area (deer, oak trees, squirrels, humans, tadpoles)
4. ecosystem: the biotic community and its abiotic factors (all the living and nonliving things in the area)
5. biome: large areas containing several ecosystems (tundra, desert, grassland, tropical rainforest)
6. biosphere: part of Earth where life exists; the top layer of Earth’s crust, all waters, atmosphere

4.  habitat—the place in which an organism lives

1. provides the food, shelter, temperature, and moisture the organism needs for survival
2. a rotting log is a perfect habitat for insects, fungi, and worms
3. a sea star finds food and comfortable temperatures in shallow ocean water

5.  niche—an organism’s role or how it acts in its environment

a.       how it gets food; some animals eat other animals; some only eat plants

b.      how it avoids danger; defends itself; hides from a predator

c.       finds a mate

d.      cares for its young

e.       predator—consumer that captures and eats other consumers

f.        prey—the organism that is captured by the predator

Populations

1. competition—two or more organisms seek the same resource at the same time
   1. deer, rabbits, and grasshoppers competing for grass in an area
2. Population size—indicates whether a population is healthy and growing
   1. population density---number of individuals in a particular area
   2. carrying capacity—the largest number of individuals of one species that an ecosystem can support; based on limited food and limited space
   3. limiting factor---biotic or abiotic factors that restricts the size of a population
   4. biotic potential—the size a population could reach if no limiting factors stopped its growth
3. Elements that affect population size---
   1. birth and death rates
   2. movement of organisms into or out of an area
   3. fishing or hunting

Energy Flow

1.   photosynthesis---producers (plants, algae) convert light energy to chemical energy

·        combine carbon dioxide and water to produce glucose and oxygen

·        Cellulose is the substance that makes up most of a plant's cell walls. An increase in the cellulose is an increase in plant size.

6CO₂   +   6H₂O   +   energy ®   C₆H₁₂O₆   +   6O₂

a.    chemosynthesis—the production of energy-rich nutrient molecules from chemicals (ocean)

b.   biomass---organic material made from plants and animals (microorganisms)

2. Energy transfer----

a.       food chains—shows how matter and energy pass from one organism to another

b.      food web—shows all the possible feeding relationships among the organisms

c.       energy pyramid—shows the amount of energy available at each feeding level in an ecosystem

d.      trophic level---each feeding level in an ecosystem

Ø      organisms at each trophic level get energy by feeding on organisms at a lower level

Ø      the flow of energy moves through the chain, web or pyramid

Ø      only about 10% of the energy at one trophic level is passed on to organisms at the next trophic level

e.       energy flow---arrows represent the pathway of the energy

Ø      final consumer has the smallest percentage of original energy available

Ø      the first producer has the largest percentage of energy

f.        primary consumer---feeds directly on producers

g.       secondary consumer---feeds on primary consumers

h.       tertiary consumer---feeds on secondary consumers

Interactions within Communities

1. sun—source of energy that fuels most life on Earth
2. producers (autotroph)—an organism that makes its own food using photosynthesis

a.       plants, many algae, and some bacteria

b.      most producers use the sun and contain chlorophyll, a chemical required  for photosynthesis

3. consumers (heterotroph)—organisms that cannot make their own energy-rich molecules; they obtain energy by eating other organisms

a.       herbivores---deer and rabbits; obtain energy by feeding or eating plants

b.      carnivores---frogs and lions; eat animals

c.       omnivores---pigs and humans; eat both plants and animals

d.      scavengers--- animals that feed on the bodies of dead animals (vultures, lobster, crayfish)

4. decomposers---earthworms, fungi and bacteria eat dead organisms
   1.  the removal of decomposers would have a big impact on the recycling of nutrients
5. symbiosis—close interactions between species
   1. mutualism---both species benefit

·        (honey bee and dandelion; clownfish and anemone)

2. commensalism---helps one species but has no effect on the other

·        American Robin and a Red Maple tree

·        cattle egrets and livestock

·        shark and remora

3. parasitism ---one species is harmed and the other benefits

·        white-tailed deer and deer tick

·        tapeworm and pig

Environmental Issues:

1. alien species (invasive, foreign, exotic)---invade foreign lands, where they may thrive, become pests, and threaten native species (kudzu, zebra mussel, purple loosestrife)
2. deforestation---clearing of forest lands

·        may cause the extinction of species and often leaves the soil infertile

·        contributes to greenhouse effect; soil erosion; extinction of species

3. conservation---wise use of and preservation of the Earth’s natural resources
   1. renewable and nonrenewable
4. biodiversity---variety of life on Earth
   1. vital for maintaining stable, healthy, and functioning ecosystems
   2. endangered species---threatened
   3. extinction---no longer exist
5. Rachel Carson---biologist, founder of the modern environmental movement about pesticides
6. Jane Goodall---expert on chimpanzees; worked on conservation and animal welfare issues

Additional Diagrams---