CHAPTER 5 BIODIVERSITY, SPECIES INTERACTIONS, & POPULATION CONTROL

Why care about sea otters?

• Ethics
• Tourism dollars
• Keystone species

Five types of species interactions affect the resource use and population sizes of the species in an ecosystem:

• Competition
• Predation
• Parasitism
• Mutualism, and
• Commensalism

Competition

is the common use of a resource in short supply.

interspecific Competition

is competition between individuals of different species

Intraspecific Competition

is competition between individuals of the same species.

There are many ways that organisms reduce
competition. For example

hunting at night instead of during the day, stratification, marking territories, etc.

Competitive Exclusion Principle

No two species can have the exact same niche.
 One will be a better competitor and eliminate the other.

Resource partitioning

• Using only parts of the resource
• Using at different times
• Using in different ways

example of resource partitioning

Predation

is when one species feeds on another

Predators have evolved many methods to capture prey. For example

cooperation, speed, etc.
 Prey tend to be old, sick, disabled, etc.

Prey may avoid capture by

1. Speed - run, swim, fly

   2. Protection: shells, bark, thorns
   3. Camouflage
   4. Poison - chemical warfare
   5. Warning coloration
   6. Mimicry
   7. Deceptive looks
   8. Deceptive behavior

Predators may capture prey by

1. Speed – walking, swimming, flying
2. Pursuit and ambush
3. Camouflage
4. Chemical warfare
5. Cooperation

prey tend to be

old, sick, disabled, etc.

Coevolution

the simultaneous evolution of two species

The evolution of one species in the coevolution relationship is partially dependent on the

evolution of the other

examples of coevolution

pollinators and flowers.
 Bats and moths: echolocation of bats and sensitive hearing of moths, fuzz on moths

Parasitism

 Parasite is usually much smaller than the host
 Parasite rarely kills the host
 Parasite-host interaction may lead to coevolution
 Both plants and animals have parasites.

Mutualism

Is a relationship between two species in which both benefit.

examples of Mutualism

• Flowers & their pollinators
• Nutrition
• Protection relationship
• Gut inhabitant mutualism

Hummingbirds and Flower, Oxpeckers and Black Rhinoceros, Clownfish & Sea Anemones

Commensalism

Is a relationship between two species which is beneficial to one, but neutral or of no benefit to the other

examples of commensalism

• barnacles on whales
• epiphytes
• birds nesting in trees
• remoras on sharks

Range of tolerance

is the range of physical and chemical conditions that must be maintained for populations or a particular species to stay alive and grow normally

Each organism has a particular range of

tolerance

Limiting factor principle

Too much or too little of any physical or chemical factor can limit or prevent the growth of a population, even if all other factors are at or near the optimal range of tolerance

Limiting Factor

Is the single factor that limits the growth abundance or distribution of a particular organism in the ecosystem

A limiting factor can be

too much or too little temperature, water, sunlight, nutrients, etc

in aquatic ecosystems, examples of limiting factors are

salinity and dissolved oxygen content.

Population change

(births + immigration) – (deaths + emigration)

Population crash

A population exceeds the area’s carrying capacity
 Reproductive time lag may lead to overshoot

Damage may reduce area’s

carrying capacity

Carrying capacity (K)

Maximum population a given habitat can sustain

A population can exceed its habitat’s carrying capacity and

crash

Ecological Succession

is the replacement of one community by another.

Ecological Succession example

take a new volcanic island or a forest cleared by man

First come the pioneer species

the first step in succession They invade or colonize the area, and usually create soil from rock.
 This makes the environment more suitable for other species

The mature or climax community

is the stable, end community of succession that is capable of self-perpetuation.

There are two kinds of succession:

• Primary Succession
• Secondary Succession

Primary succession

is the sequential development of communities in a bare area that has never been occupied by a community of organisms.

Examples of primary succession

sand dunes, bare rock, volcanic island
• No soil in a terrestrial system
• Takes hundreds to thousands of years
• Need to build up soils/sediments to provide necessary nutrients

Secondary succession

is more common, is
the sequential development of communities in
an area in which natural vegetation has been
removed or destroyed (some soil remains).

Secondary succession also occurs to

ponds as they fill and are converted to forests.

examples of secondary succession

abandoned farmland, cut or burned forests, disturbed ecosystems.

Property

complexity, energy source, waste production, nutrients, net primary productivity

Natural systems

biologically diverse, renewable energy, litter, if any, recycled, shared among many species

Human dominated systems

Biologically simplified, mostly nonrenewable fossil fuel energy, high, often lost of wasted, used destroyed or degenerated to support human activities