1. Ecosystems

2. The Nature of Ecology
Biology is a natural science concerned with the study of life and living organisms
Ecology is the study of connections in the natural world
Ecologists try to understand interactions among organisms, populations, communities, ecosystems, and the biosphere.

3. Levels of Organization of Matter in Nature

4. What are Organisms? An organism is any form of life.
The cell is the basic unit of life in organisms.
Organisms are classified as either:
Prokaryotic – organisms without nucleus
Bacteria
Eukaryotic – organisms with nucleus
All organisms except bacteria

5. Classification of Organisms

6. What are Species?
Species – a group of organisms that is distinct from other groups in its morphology, behavior, or biogeochemical properties.
Species differ in how they produce offspring:
Asexual reproduction is a mode of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only
Primary form of reproduction for single-celled organisms such as the archaebacteria, eubacteria, and protists. Many plants and fungi reproduce asexually as well.
Sexual Reproduction is a process that creates a new organism by combining the genetic material of two organisms.
Primary form of reproduction for humans and the majority of other eukaryotes — plants as well as animals.

7. Populations
Population – A group of organisms of the same species that live in the same area.
Examples: (1) sunfish in a pond, (2) white oak trees in a forest, and (3) people in a country.
In response to environmental conditions, populations change in (1) size, (2) age distribution (# of individuals in each age group), (3) density (# number of individuals per unit of space), and (4) genetic composition.
Habitat is the place where a population (or an individual organism) normally lives.

8. Communities, Ecosystems, & Biosphere
Community – All of the populations of organisms within a given area
Ecosystem – All organisms and nonliving entities that occur and interact in a particular location.
Biosphere – is the portion of the earth in which living (biotic) organisms exist and interact with one another and with their nonliving (abiotic) environment).
All of the earth’s ecosystems together make up what we call the biosphere.

9. Biosphere
Biologists have classified the terrestrial (land) portion of the biosphere into biomes.
They are large regions such as forest, deserts, and grasslands characterized by (1) a distinct climate and (2) specific life-forms (especially vegetation) adapted to it.
Marine and freshwater portions of the biosphere divided into aquatic life zones, each containing numerous ecosystems.
Aquatic equivalent of biomes
Examples include (1) freshwater life zones (such as lakes and streams) and (2) ocean or marine life zones (such as estuaries, coastlines, coral reefs, and the deep ocean).

10. Major Abiotic (Nonliving) Components
Terrestrial Ecosystems
Sunlight
Temperature
Precipitation
Wind
Latitude
Altitude
Fire Frequency
Soil
Aquatic Life Zones
Light penetration
Water currents
Dissolved nutrient concentrations
Suspended solids
Salinity

11. Major Biotic (Living) Components
Living organisms in ecosystems usually are classified as either producers or consumers, based on how they get their food.
Producers, sometimes called autotrophs (self-feeders), make their own food from compounds obtained from their environment.
On land:
Most producers are green plants
In freshwater and marine ecosystems:
Algae and plants are major producers near shoreline
In open water the dominant producers are phytoplankton

12. Photosynthesis & Chemosynthesis
Photosynthesis – the process of turning the sun’s diffuse light energy into concentrated chemical energy
Sunlight converts carbon dioxide and water into sugars
A few producers, mostly specialized bacteria, can convert simple compounds from their environment into more complex nutrient compounds without sunlight, a process called chemosynthesis.

13. Photosynthesis Produces Food
Chloroplasts – organelles where photosynthesis occurs
Contain chlorophyll – a light-absorbing pigment
Light reaction – splits water by using solar energy
Calvin cycle – links carbon atoms from carbon dioxide into sugar (glucose)
This initiates a complex series of chemical reactions in which carbon dioxide and water are converted to sugars and oxygen.

14. Light and pigments

15. Consumers
Consumers or heterotrophs get their food by eating or breaking down all or parts of other organisms or their remains.
Animals, fungi, microbes
Herbivores (plant eaters)
Primary consumers that eat producers
Carnivores (meat eaters)
Primary consumers eat primary consumers
Third and higher level consumers: carnivores that eat carnivores
Omnivores (such as pigs, rats, foxes, bears, and humans)
Feed on both plant and animals

16. Decomposers
Scavengers (such as vultures, flies, hyenas, and some species of sharks, & ants)
Feed on dead organisms
Detrivores (such as crabs, carpenter ants, termites, & earthworms)
extract nutrients from partly decomposed organic matter in leaf litter, plant debris, and animal dung
Chemical Decomposers (mostly certain types of bacteria and fungi)
recycle nutrients in ecosystems.

17. Aerobic Respiration
Organisms break down carbohydrates and other organic compounds in their cells to obtain the energy they need.
This is usually done through aerobic respiration.
The opposite of photosynthesis

18. Anaerobic Respiration
Anaerobic respiration or fermentation:
Some decomposers get energy by breaking down glucose (or other organic compounds) in the absence of oxygen.
The end products vary based on the chemical reaction:
Methane gas
Ethyl alcohol
Acetic acid
Hydrogen sulfide

19. Cellular Respiration releases chemical energy
It occurs in all living things
Organisms use chemical energy from photosynthesis
The energy is used for cellular tasks
C6H12O6 (sugar) + 6O CO2 + 6H2O + energy

20. Photosynthesis and cellular respiration

21. Energy Flow thru Ecosystems
The one-way flow of high-quality solar energy through materials and living things (as they eat) produces low-quality energy.
Ecologists assign every type of organism in an ecosystem to a trophic or feeding level.
Energy flows from one trophic level to another.

24. Food Chains
Food chains follow a single path as animals eat each other.
Example:
THE SUN provides food for GRASS
The GRASS is eaten by a GRASSHOPPER
The GRASSHOPPER is eaten by a FROG
The FROG is eaten by a SNAKE
The SNAKE is eaten by a HAWK. 

26. Food Web
Food webs show how plants and animals are interconnected by different paths. Example:
TREES produce ACORNS which act as food for many MICE and INSECTS.
Because there are many MICE, WEASELS and SNAKES have food.
The insects and the acorns also attract BIRDS, SKUNKS, and OPOSSUMS.
With the SKUNKS, OPPOSUMS, WEASELS and MICE around, HAWKS, FOXES, and OWLS can find food.
They are all connected! Like a spiders web, if one part is removed, it can affect the whole web. 
Food web show how plants and animals are connected in many ways to help them all survive. Food chain follow just one path of energy as animals find food. 

27. Levels of Food Chains/Webs
Primary producers/1st trophic level
Transform energy from sun or chemicals
Primary consumers/2nd trophic level
Herbivores
Secondary consumers/3rd trophic level
Carnivores
Tertiary consumers/4th trophic level
Top carnivores
Decomposers
Feed on nonliving organic matter
Feces/dead organisms
In the first, or lowest, trophic level are the primary producers. Primary producers transform energy from sunlight or certain inorganic chemicals into high-energy carbohydrates. Green plants, algae, and cyanobacteria, as well as chemosynthetic bacteria found in soils and deep-sea hydrothermal vents, are primary producers.
Primary producers are the ultimate source of the chemical energy used by all members of ecological communities.
Carnivores such as lions or insect-eating birds that feed directly on herbivores make up the third trophic level; they are called secondary consumers. Tertiary consumers—organisms that feed on secondary consumers—form the fourth trophic level. You might imagine such a feeding chain extending indefinitely. But in fact, communities with more than four trophic levels are quite rare, for reasons that will soon become clear. 27

28. Marine Food Web Marine Food Web
TERTIARY
CONSUMERS
Gull
Tuna
Seal
Flounder
Egret
SECONDARY
CONSUMERS
Plover
Herring
Blue Crab
CONSUMERS
PRIMARY
Mussles
Zooplankton
Fiddler Crab
Clams
Marine Food Web
Marine food webs are often quite complex. The thickness of arrows refers to relative amounts of energy transferred among food web members.
Live Grasses
Spartina Grasses
PRODUCERS
PRIMARY
Key
Live Algae
Marina Algae
Dead body
decomposes
and reenters
the food
chain.
Phytoplankton
The thicker the
arrow, the
greater the
amount of
energy
transferred
among food
web
members.
DEATH
AND DETRITIVORES
DECOMPOSERS
Aquatic Bacteria
(Decomposer)
Shrimp
(Detritivore)
Water mold
(Decomposer) 28

29. Terrestrial Food Web Terrestrial Food Web
Black Rat
Snake
Red Tailed
Hawk
Fox
TERTIARY
CONSUMERS
Goldfinch
SECONDARY
CONSUMERS
Bluebird
Vole
Blackbird
Insects
CONSUMERS
PRIMARY
Snail
Terrestrial Food Web
Because plants produce large quantities of wood and cellulose that cannot be digested by herbivores, much energy in terrestrial food webs is processed by decomposing organisms. Like birds feeding on worms, decomposers may then be consumed by predators.
Key
Trees
Ferns
Dead body
decomposes
and reenters
the food
chain.
PRODUCERS
PRIMARY
Moss
Grass
Plants
The thicker the
arrow, the
greater the
amount of
energy
transferred
among food
web
members.
DEATH
Fungi (Decomposer)
Soil bacteria
(Decomposer)
AND DETRITIVORES
DECOMPOSERS
Earthworms
(Detritivores) 29

30. Biomass
Biomass is the total dry weight of the organisms in a trophic level.
In a food chain or web, chemical energy stored in biomass is transferred from one trophic level to another.
With each transfer some usable energy is degraded and lost to the environment as low-quality heat.

31. Losing Energy in Food Chains and Webs
In accordance with the 2nd law of thermodynamics, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web.
Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next.
It ranges from 5% to 20% but 10% is typical.
10% ecological efficiency means 90% loss of energy.

32. Primary Production Gross primary production (GPP)
Rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass.
Net primary production (NPP)
NPP = GPP – R
Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R).
Primary Production

33. What are nature’s three most productive and three least productive systems?

35. Two Secrets of Survival for an Ecosystem: Energy Flow and Matter Recycle