Introduction to Ecology Chapter 18

Ecology Section 18.1

Definition: The study of the interactions between organisms and their environment Interdependence of organisms and their environment

Levels of Organization 1.Biosphere 2.Ecosystem 3.Community 4.Population 5.Organism

Biosphere The Earth & the atmosphere “Thin film of life covering a lifeless planet”

Ecosystem All organisms & nonliving environment in a given place –Organisms + water, pH, minerals, etc.

Community All of the interacting organisms in an ecosystem –Living things only!

Population All the members of ONE species living in one place at one time

Organism ONE member of ONE species living in one place at one time

Ecology of Organisms Section 18.2

Habitat Where organisms live Contains abiotic and biotic factors –Abiotic: nonliving components Ex) sunlight, water, soil –Biotic: living components Ex) plants, animals, predators

Tolerance Range The range of abiotic conditions where the organism can still perform all activities for life A B C C A & C = poor performance B = peak performance

Acclimation When an organism adjusts its tolerance to an abiotic factor Ex) Moving from room to room with different temperatures

Control of Internal Conditions Conformers: organisms that DO NOT regulate their internal environment –“cold blooded” Regulators: organisms that DO regulate their internal environment –“warm blooded”

Escape from the Habitat Dormancy: a state of reduced activity for the organism –Hibernation Migration: movement of organism to a favorable habitat –Immigration: movement into a habitat –Emigration: movement out of a habitat

Niche The way of life for a species The role the species plays on its environment

Niche includes: Tolerable conditions for organism Methods to obtain resources Number of offspring per year Time of reproduction Any other interactions with the environment ETC.

2 Types of Niches Fundamental Niche: the range of conditions a species could POTENTIALLY tolerate and the range of resources it could POTENTIALLY use. Realized Niche: the range of conditions and resources the species ACTUALLY tolerates and uses.

Questions: Which niche is larger? Why?

Niche Differences A species’ niche can change within its lifespan Generalist: species with a broad niche Specialist: species with a narrow niche Specialist Generalist

Question: Which type can adapt to a changing environment better? –Generalist or specialist? Why?

18-3 Energy Transfer Energy  Why do organisms need energy?  Maintain HOMEOSTASIS, growth, reproduction, etc.  How does energy affect an ecosystem?  Determines how many and what kind of organisms live in an ecosystem.

Energy Flow: The sun is the ultimate source of energy The PRODUCERS use this energy to make “food” energy for themselves and for the CONSUMERS

Trophic Levels  The organism’s position in the sequence of energy transfers.  A.K.A. Trophic Level is a group of organisms whose feeding source is the same number of steps from the Sun.

Common Trophic Levels: First = Producers (Autotrophs) –LARGEST Second = Herbivores (Heterotrophs, Consumers) Third and above = All other consumers (Heterotrophs, Omnivores, Carnivores, Decomposers) –SMALLEST

Omnivores (Humans)Omnivores (Humans) –Eat Plants & Animals Detritivores (Scavengers)Detritivores (Scavengers) –Feed On Dead Plant & Animal Remains (buzzards) DecomposersDecomposers –Fungi & Bacteria

Consumers Heterotrophs eat other organisms to obtain energy. (e.g. animals) HerbivoresHerbivores –Eat Only Plants CarnivoresCarnivores –Eat Only Other Animals

Energy Gain by Trophic Levels: At each trophic level, the energy stored in an organism is about 1/10 that of the level below it (10%).

Implications on the ecosystem:  Because energy diminishes at each successive trophic level, few ecosystems can contain more than 4 or 5 trophic levels.  Organisms at higher levels (large carnivores) tend to be fewer in number than those at lower levels (producers).

Food Chain A single pathway of feeding (and energy transfer) relationships among organisms in an ecosystem.

Ex) Food chain

Food Web A diagram of the interrelated food chains in an ecosystem. More accurate description of the ecosystem.

Can you now answer these questions? 1.Contrast between producers and consumers. 2.Explain the important role of decomposers in an ecosystem. 3.Explain why an ecosystem usually contains only a few trophic levels. 4.What is the difference between an organism’s niche and its habitat? 5.List 2 sources that add carbon to the carbon cycle.

Energy flows through an ecosystem and nutrients cycle in an ecosystem. Ecosystem Recycling (18.4)

Water Cycle Steps:  EVAPORATION from lakes, rivers, and oceans.  TRANSPIRATION from plants and trees.  CONDENSATION – Cloud Formation  PRECIPITATION – Rain, Snow, Sleet, Hail.  RUN OFF, or RETURNED back into the Cycle.  Groundwater- water in soil or in underground formations of porous rock.

The Water Cycle

The Carbon Cycle  Cellular Respiration  Photosynthesis  Combustion  Death and decomposition

Human Influences  Atmospheric CO2 has risen more than 30% in the past 150 years.  Burning of fossil fuels- coal, oil, and natural gas  Burning down the tropical rain forest

The Nitrogen Cycle Nitrogen Fixation: the process of converting atmospheric nitrogen (N2) into nitrate, its useable form.

Nitrogen-fixing bacteria: turn nitrogen gas into a useable form. Located in soil and the roots of some plants. Ammonification: bacteria decompose dead matter and release the nitrogen they contain as ammonia Key Terms So… How do plants and animals get nitrogen?

Phosphorous Cycle obtained by plants from water and soil, and animals from the food they eat used to form bones, teeth, and molecules such as DNA and RNA Source: erosion of rocks into the soil or water, decomposition of organisms, and fertilizers