1.1: Introduction to ecology

Ecology

studies the relationships among living organisms and their environment

Ecology Hierarchy

• Biosphere (largest)

• Biome

• Landscape

• Ecosystem

• Community

• Population (species)

• Organism or Species (individual) (smallest)

Ecosystem

A community of living (biotic) organisms interacting with the non-living (abiotic) components of their environment as a system through various nutrients and energy cycles.

Abiotic factors

are the nonliving parts of an ecosystem.

• Rocks, air, water, sand, etc.

Biotic factors

are living things in an ecosystem.

• Plants, animals, bacteria, etc.

Population

Organisms of the same species that interact with each other and occupy a specific area

Community

Population of different species.

Species

Organisms that resemble each other, are similar in genetic makeup, chemistry, and behavior, and are able to interbreed and produce fertile offspring.

Specialists

species that have a narrow niche and can therefore only live in very specific areas/habitats

Generalists

species that have a broad niche, highly adaptable, can live in varied habitats

Niche

An animal's "niche" is a description of what an animal's role in an ecosystem. It includes:

• Resources it uses

  • Habitat

  • food

• Behavior

  • When are they awake/active?

  • When do they mate?

• Interactions with other animals

  • What animals do they kill?

  • What animals kill them?

Competition

arises when 2 (or more) individuals of the same or different species are competing for resources in the environment.

• Competition affects BOTH organisms involved in a negative way.

Interspecific Competition

Two different species compete for the same resource

Intraspecific Competition

Two organisms from the same species compete for a resource

Limited Resource Availability

When two species compete, they both have to share the same limited resources. This means each individual gets less of what it needs to survive and thrive.

Reduced Growth

Individuals may grow more slowly because they don't get enough food, water, or sunlight.

Decreased Reproduction

With fewer resources, organisms may not be able to reproduce as successfully, leading to lower birth rates.

Lowered Survival

Scarcity of essential resources can increase stress and make it harder for individuals to survive

The Principle of Competitive Exclusion (Gause’s principle)

States that two species or populations cannot inhabit the same niche: one will consistently out-compete the other

There are two ways you can avoid competition

• Resource Partitioning

• Niche

Resource Partitioning

Animals can choose to use these resources at different times to avoid other animals

• Examples:

  • Hunt at different times of the day

  • Breed at different times of the year

  • Feed at different depths of water

  • Live in different parts of a tree

Niche

Animals can use different resources from other animals, so they don't compete for the same resources.

• Examples:

  • Over time different species of birds in an area may evolve to eat different types of seeds and live in different trees to avoid competition.

Fundamental niche

the entire set of conditions under which an animal (population, species) can survive and reproduce itself.

Realized niche

the set of conditions actually used by given animal (population, species), after interactions with other species (predation and especially competition) have been taken into account.

Predator-prey cycles

based on a feeding relationship between two species

• If the prey species rapidly multiply, the number of predators increases until the predators eventually eat so many of the prey that the prey population dwindles again

Boom-and-bust cycles

• Prey populations rapidly increase. This is followed by an increase in the predator population.

• As predators eat the prey, their population goes down because there is less to eat and the predator population also goes down. 

Symbiosis

A close relationship between two different species

• Mutualism (+/+): BOTH species benefit from each other in this interaction.

• Parasitism (+/-): One species benefits and the other species is negatively affected.

• Commensalism (+/o): One species benefits and the other species is not affected.

• Ammensalism (-/o): One species is harmed while is other is unaffected!

Pathogen

A parasite that causes disease in its host.

Parasitoid

A specialized type of predator that lays eggs inside other organisms—referred to as its host