Competition

What is competition in ecology?

When organisms struggle to obtain the same limited resources.

What is intraspecific competition?

Competition between individuals of the SAME species.

What is interspecific competition?

Competition between DIFFERENT species.

What is indirect exploitation competition?

Organisms compete by using up a shared resource, leaving less for others.

What is direct interference competition?

Organisms directly prevent others from accessing resources.

What are the costs of direct interference?

• Risk of injury

• Lost time

• Energy used for fighting or defense

What is a shared limiting resource?

A resource that organisms need but is limited in availability.

What is a resource?

Something organisms use that can be consumed or depleted.

What is a condition?

An environmental factor that cannot be used up or depleted.

What is the main difference between resources and conditions?

Resources can be depleted; conditions cannot.

What is a niche?

All the environmental conditions and resources a species needs to survive and reproduce.

How can competition affect geographic distribution?

Competition can prevent species from living in places where they could otherwise survive.

How do scientists test whether two species compete?

Compare their growth, fitness, or population density when grown alone versus together.

What happens to carrying capacity (K) when competition increases?

Carrying capacity often decreases because fewer resources are available.

What is a fundamental niche?

The full range of conditions and resources a species COULD use without competition or other limiting biological interactions.

What is a realized niche?

The smaller portion of the fundamental niche a species ACTUALLY occupies because of competition and other interactions.

What is the difference between fundamental and realized niches?

Fundamental = Where a species could live. Realized = Where a species actually lives.

What are the two possible outcomes of competition

• Competitive exclusion: One species loses and disappears.

• Coexistence: Both species survive together.

What does asymmetrical competition mean?

One species is a stronger competitor and affects the other more.

What two organisms competed in Tilman's experiment?

Synedra and Asterionella (diatoms).

What resource were the diatoms competing for?

Silica, which is used to build their cell walls.

Which diatom was the stronger competitor?

Synedra.

Why did Synedra outcompete Asterionella?

Synedra could survive at lower silica levels, reducing silica below what Asterionella needed.

What type of competition was demonstrated?

Indirect exploitation competition because Synedra depleted the shared silica resource.

What resource were kangaroo rats and ants competing for?

Seeds

Why can rodents and ants coexist?

Resource partitioning: They use different seed sizes, reducing competition.

Which lizard is the strongest ground competitor?

Brown anole.

Which lizard is the strongest canopy/vegetation competitor?

Day gecko.

Why is the green anole struggling in Hawaii?

Brown anoles dominate the ground, while day geckos dominate vegetation, leaving less available space and resources for green anoles.

How does competition affect population abundance?

Populations often have lower densities when competing than when living alone.

What is resource partitioning?

When species use different parts of a shared resource to reduce competition.

What is character displacement?

When competing species evolve different physical traits over generations to reduce competition.

How does competition affect evolution?

It favors traits that reduce resource overlap and help organisms compete.