Ecologythe scientific study of interactions between organisms and their environments, focusing on energy transfer
• It is a science of relationships.

What do you mean by environment?
The environment is made up of two factors:
Biotic factors - all living organisms inhabiting the Earth
Abiotic factors - nonliving parts of the environment (i.e. temperature, soil, light, moisture, air currents)

• Water – Essential to all living things.
• Sunlight – Necessary for photosynthesis.
• Oxygen – Essential to most living things.
• Temperature –Determines the type of organisms in an area.
• Soil – Affects plant growth, shelter, and bacteria.

Population
Organism

Organism
any unicellular or multicellular form exhibiting all of the characteristics of life, an individual.
•The lowest level of organization

Population -
a group of organisms of one species living in the same place at the same time that interbreed and compete with each other for resources (ex. food, mates, shelter)

Community
several interacting populations that inhabit a common environment and are interdependent.

Ecosystem -
All living and non-living things in a given area that interact with one another.
–Can be large or small

Biosphere
- life supporting portions of Earth composed of air, land, fresh water, and salt water.
•The highest level of organization

“The ecological niche of an organism depends not only on where it lives but also on what it does. By analogy, it may be said that the habitat is the organism's ‘address’, and the niche is its ‘profession’, biologically speaking.”
Odum - Fundamentals of Ecology

Niche - the role a species plays in a community (job)
Habitat - the place in which an organism lives out its life
(address)

Habitat vs. Niche
A niche is determined by the tolerance limitations of an organism, or a limiting factor.
Limiting factorany biotic or abiotic factor that restricts the existence of organisms in a specific environment.

Habitat vs. Niche
Examples of limiting factors-
•Amount of water
•Amount of food
•Temperature

• The flow of energy through an ecosystem begins with the sun, and is passed on through various organisms:
• The energy of the sun begins the flow of energy for living
Sun

Producers

Consumers

Decomposers

Energy Pathway
• Producer- autotrophic organisms that are able to make their own food. Most producers perform photosynthesis
(making food from the sun) or chemosynthesis (making food from inorganic compounds).
•
Examples : aquatic plants, algae, phytoplankton

Energy Pathway
• Consumer- heterotrophic organisms that get energy by eating producers or other consumers.
•
Examples : aquatic invertebrates, fish
• Carnivores
• Omnivores

• Carnivores – eat meat
• Invertivores – eat invertebrates
• Planktivores – eat zooplankton
• Omnivores – eat lots of things

Consumers can be at different levels, depending on the specific food chain.

Energy Pathway
Decomposers – obtain energy from the remains of other organisms.
Decomposers are most important for the recycling of matter within ecosystems.
Examples : crabs, lobsters, bacteria

Types of Consumers
Primary Consumers
First level of consumers that eat producers These are all herbivores (or planteaters)
Ex . Zooplankton, some aquatic invertebrates, some fish

Types of Consumers
Secondary consumers
Second level of consumers that eat primary consumers.
These are carnivores
(meat eaters), invertivores (eat invertebrates), planktivores (feed on zooplankton), or omnivores (feed on a variety of things)

Types of Consumers
Tertiary (Top)
Consumers
Higher level consumers that begin at the third level or higher.
Tertiary consumers are usually those at the top of the food chain in that ecosystem.
Ex . Bass, turtles, snakes, alligators

Types of Consumers
Decomposers
Detritivores – heterotrophic organisms that get energy by shredding and eating detritus
(non-living organic matter, ie: bodies of dead things). These are the scavengers of aquatic ecosystems.
Examples : most bottom dwelling organisms
Bacteria and fungi – these break down remaining particles into the tiniest units to release nutrients for use by producers

There are 3 main types of feeding relationships:
1. Producer- Consumer
2. Predator- Prey
3. Parasite- Host

Symbiotic Relationships
Symbiosistwo species living together
3 Types of symbiosis:
1. Commensalism
2. Parasitism
3. Mutualism

Symbiotic Relationships
Commensalismone species benefits and the other is neither harmed nor helped
Example : Relationship between small fish and the pond weeds; the fish hide between the weeds from larger fish. Another relationship is the one between oysters and the mangrove trees.
The oyster anchor and protect themselves with the roots of the tree .

Symbiotic Relationships
Parasitismone species benefits (parasite) and the other is harmed (host)
• Parasite-Host relationship
• Example:
Freshwater Ich, a protozoa that infects fish

Symbiotic Relationships
Parasitismparasite-host
Ex. lampreys, leeches, fleas, ticks,tapeworm

Symbiotic Relationships
Mutualismbeneficial to both species
Example: some small fish enter & clean the mouths of larger fish, and in exchange, they may eat whatever they clean out.
Cleaner Shrimp

Type of relationship
Commensalism
Species harmed
Parasitism
Mutualism
Species benefits
Species neutral
= 1 species

Food Chains & Food Webs
All organisms are interconnected by food chains, and play an important role in their ecosystem’s food web
Food chainare the feeding relationships between individual organisms.

Food Chains & Food Webs
Food webs are all of the interconnecting food chains in an ecosystem .
A change in the populations of one organism in a food chain can seriously alter all other organisms of the food web!

Trophic Levels
• Each link in a food chain is known as a trophic level.
• Trophic levels represent a feeding step in the transfer of energy and matter in an ecosystem.

A limit is reached when consumers cannot consume enough energy to balance energy lost during normal physiological functions
(growth, reproduction). Most ecosystems have about four to five trophic levels.
•
Note : An organism can be at varying trophic
levels (feeding level) of a food web, depending on the specific food chain you are examining. A change in the population of one organism or one trophic level in a food chain can seriously alter all other organisms of the food web.

Food Web:
• In any ecosystem, most organisms have more than one source of food.
For example, a large fish may feed on smaller fish, crayfish, and insects.
This process results in an organism being part of more than one food chain. The complex overlapping of food chains is known as a food web

Food chain
(just 1 path of energy)
Food web
(all possible energy paths)

Part 4: Ecological Pyramids
• Diagrams showing the relative amounts of energy or matter contained within each trophic level in a food chain.
– 3 types
• Pyramid of Energy
• Pyramid of Biomass
• Pyramid of Numbers

• shows how energy flows through a food chain from trophic level to trophic level. Most of the energy an organism obtains is used for its life processes (reproduction, respiration, growth, etc.) Only about 10% is available to the next higher organism that eats it.
• The nutritional quality of material that is eaten also influences how efficiently energy is transferred, because consumers can convert high-quality food sources into new living tissue more efficiently than low-quality food sources

E
R
E
N
G
Y
Trophic Levels
Tertiary consumers- top carnivores
Secondary consumerssmall carnivores
Primary consumers- Herbivores
Producers- Autotrophs

Trophic Levels
Biomassthe amount of organic matter comprising a group of organisms in a habitat.
• As you move up a food chain, both available energy and biomass decrease.
• Energy is transferred upwards but is diminished with each transfer.

How many trophic levels can an ecosystem support?
• This depends on several factors:
• the amount of energy entering the ecosystem
• energy loss between trophic levels
• the form, structure, and physiology of organisms at each level.
– Predators at higher trophic levels are generally physically larger than organisms at lower levels, so they have to forage over increasingly large areas to meet their energy needs.

• Because of energy losses , most land ecosystems don’t have more than
5 trophic levels. Marine ecosystems generally have no more than 7 . This difference is most likely due to the differences between the producers of these two ecosystems. In marine ecosystems, microscopic phytoplankton carry out most of the photosynthesis, while plants do most of this on land.

• Phytoplankton are extremely small with very simple structures, so most of their primary energy production is consumed and used for energy by the primary consumers that feed on them. Land plants, however, have large amounts of unusable parts in terms of providing a source of energy to what eats them. The roots, trunks, and branches of plants cannot be used for food (by most organisms), so less of the energy produced by those plants travels up the food chain

• An important consequence of the loss of energy between trophic levels is that contaminants collect in animal tissues
—a process called bioaccumulation , or biological magnification . As contaminants bioaccumulate up the food web, organisms at higher trophic levels can be threatened even if the pollutant is introduced to the environment in very small quantities.

• The insecticide DDT , which was widely used in the United States from the 1940s through the 1960s, is a famous case of bioaccumulation. DDT built up in eagles and other large predatory birds to levels high enough to affect their reproduction, causing the birds to lay thin-shelled eggs that broke in their nests. Fortunately, populations have rebounded over several decades since the pesticide was banned in the United States. However, problems persist in some developing countries where toxic bioaccumulating pesticides are still used.

• Bioaccumulation can threaten humans as well as animals. For example, in the United
States many federal and state agencies currently warn consumers to avoid or limit their consumption of large predatory fish that contain high levels of mercury, such as shark, swordfish, tilefish, and king mackerel, to avoid risking neurological damage and birth defects.