Introduction to symbiotic relationships between species in an ecosystem

1. Symbiotic Relationships
Biology
Mrs. Neistadt

2. *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.

3. Species Interactions
• *There are 5 major types of symbiotic
relationships:
– *Predation
– *Parasitism
– *Competition
– *Mutualism
– *Commensalism

4. *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

5. *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

6. 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

7. *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

8. 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

9. *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.

10. 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

11. *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

12. 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

13. *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.

14. *Commensalism
• *Commensalism is a symbiotic
relationship where one organism benefits
and the second is neither harmed nor
helped.
• Ex: *Whales and Barnacles
– Barnacles have the benefit of moving through
waters attached to the whale
– The whale receives no benefit,
but is not harmed either

15. 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