Species InteractionsSection 2-1

Species Interactions

• Species within a community develop close interactions, known as symbiosis.

– “Sym” means together– “Bio” means life– Symbiosis means “living together” and describes the

close relationships developed between species.

• Symbiotic relationships will always benefit at least one organism involved.

Species Interactions

• There are 5 major types of symbiotic relationships:

– Predation– Parasitism– Competition– Mutualism– Commensalism

Predation

• Predation is a relationship where one organism captures and consumes another.– Predator – organism doing the capturing– Prey – organism being captured

• A predator’s survival depends on its ability to catch its prey. – Ex: rattlesnake venom, spider web, etc.

• A prey’s survival depends on its ability to avoid being caught.– Camouflage, mimicry, physical/chemical defenses

Prey Defenses

• Mimicry – a defense where one organism resembles another that is dangerous or poisonous

• There are two types of mimicry:– A harmless organism closely resembles a dangerous one

• Known as Batesian mimicry• Predators learn to avoid both species• Ex: King snake and coral snake

– Two harmful organisms resemble one another• Known as Mullerian mimicry• Added advantage to their already harmful adaptations• Ex: Bees and wasps have similar striping

Prey Defenses

• Plants have also developed adaptations to protect them from predators.

– Physical defenses make them difficult to eat• Ex: Spines, thorns, tough leaves

– Can produce secondary compounds• Secondary compounds are synthesized from

products of the plant’s metabolism• Usually poisonous, irritating, or bad-tasting• Ex: Poision ivy and poison oak

Parasitism

• Parasitism – symbiotic relationship where one organism is harmed and the other is helped– Parasite feeds on the host organism– Unlike predation, it does not result in the

immediate death of the host• Ex: tapeworms can live in human digestive tract for

long periods of time

Parasitism

• There are 2 different types of parasites:

– Ectoparasites• External parasites – live on the outside of the host • Ex: ticks, fleas, mosquitoes

– Endoparasites• Internal parasites – live inside the host’s body• Ex: bacteria, protists, tapeworms

Competition

• Competition – the use of the same limited resource by two or more species in the same place at the same time

– Resource = anything necessity of life (water, nutrients, light, food, or space)

• Competition may cause the development of different niches or physical characteristics.

Competition• Competitive Exclusion Principle

– No two species can occupy the same niche in the same habitat at the same time

– Ex: Paramecia• Two species of paramecia will thrive separately, but when put together, one species is

eliminated

Competition• Organisms may develop physical differences

because of competition for resources.• Character Displacement – evolution of anatomical

differences that reduces competition– Happens most where ranges of competitors overlap

– Ex: Darwin’s finches• Species found in separate locations have the same beak size• The same species found together have different beak sizes

– allows them to feed on different seeds and reduces competition

Competition• Organisms may develop differences in niches

because of competition for resources.• Resource Partitioning – species coexist by

using only part of the available resources– Ex: some birds eat the same insects, but hunt for

them in different places

Mutualism

• Mutualism is a symbiotic relationship where both organisms are helped in some way.

• Ex: Plants and their pollinators– Pollinators feed on the plants and pollen gets

stuck to them.– Pollen is deposited on the next plant, allowing

the plants to reproduce sexually.

Commensalism

• Commensalism is a symbiotic relationship where one organism benefits and the second is neither harmed nor helped.

• Ex: Clownfish and sea anemone– The clownfish uses the anemone as shelter– The anemone receives no benefit, but is not

harmed either– animation

Name the Symbiotic Relationship…• A eagle hunting a mouse.

– Predation• A tick feeds on the blood of its host and may carry disease

– Parasitism• The flower lives on a tree and absorbs the water from runoff

and the tree is unaffected.– Commensalism

• Two different types of finches feeding on seeds.– Competition

• An ant protects a caterpillar from predators and the caterpillar produces a sweet liquid for it to drink.– Mutualism