1. Community Interactions
Section 12.1

2. Introduction
Biomes may be very different but they have something important in common.
They all have populations of interacting species.
Species interact in the same ways in all biomes.
All biomes with have predators and prey.

3. What is a Community? Community is the biotic part of an ecosystem.
It is all of the populations of all the species in an area.
All of these populations interact.
This is an important part of natural selection.

4. Community Interactions
There are three major types of community interactions:
Predation
Competition
Symbiosis

5. Predation
Predation – relationship where one species eats another species.
Predator – organism that eats the other.
Prey – organism that is eaten.
Example: Lion eating Zebra

6. Predator prey
In this Predator-Prey relationship, the spider is eating an insect that it has trapped.

7. Predator-Prey
In a predator-prey relationship one organism benefits and the other is killed.

8. The Ultimate Predator – a Wildcat!

9. Predation and Population
Predator-prey relationships keep the populations of both species in balance
Limiting factor – limits the growth of an organism, population or process.

10. Keystone Species
Keystone species – a species that is especially important to its community.
Example: sea stars and coral reefs
Predators to mussels and sea urchins that have no other predators

11. Adaptations to Predation
Predators and prey adapt and evolve through natural selection.
One example is camouflage.

12. Competition The two flowering plants are competing for the same space
Which
means both
of them are
harmed.

13. Competition
Competition is when two organisms use the same space and resources at the same time.
Intraspecific Competition - occurs between organisms of the same species
Interspecific Competition – occurs between organisms of different species
Competitive Exclusion Principle – No two species can occupy the same niche in the same habitat at the same time.

14. Kudzu Competition
Kudzu is a plant that was introduced to the United States in 1876 at the Centennial Exposition in Philadelphia, PA.
Kudzu does not have any natural predators here – therefore it grows out of control.
It “outcompetes” plants that are native so they don’t have a place to grow.
Kudzu takes over in areas where it begins to grow.
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15. Competition – introduced species
The Eastern Bluebird is being forced into smaller numbers by the House Sparrow, an introduced species.
The House Sparrow is a species of birds were introduced to our continent and remain today predators to our native birds and are territorial, aggressive, and take cavities away from our native nesters, including Bluebirds.
The House Sparrow attacks Bluebirds, including incubating females and their eggs, nestlings, and will kill and build a nest over the corpses of our native species.

16. Symbiosis
Symbiosis a close relationship between two species where at least one is benefited.
There are 3 types of symbiotic relationships:
Mutualism
Parasitism
Commensalism

17. Mutualism
Mutualism is a relationship between two organisms where both of them benefit from the relationship.
This can involve providing food, protection, a place to live or even pollination.

18. Mutualism – clownfish and anemone
The clownfish gets protection from the anemone and in
return protects the anemone from fish that would eat it
(angelfish); the clownfish also keeps the anemone free of
dirt and debris.

19. Mutualism - Lichens Lichens consist of a fungus with an algae
or photosynthetic
bacterium living
inside the fungus.
The alga provides
food for both of them
and the fungus
provides a habitat for
the alga.
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20. Mutualism – cleaner shrimp
These shrimp set up
large cleaning stations
on the reef where fish
will come to have
parasites picked from
their skin. The shrimp
gets a constant food
source and the fish (eel
in this case) gets rid of
potentially dangerous
parasites

21. Cleaner Shrimp on a Grouper

22. Mutualism – Ant and Aphid

23. The Aphid and the Ant Aphids feed on the sap of the plant they are on.
Ants use their antennae to stimulate the aphids and cause them to excrete from their abdomen a substance called honeydew which is rich in the nutrients ants require.
Each worker ant goes from aphid to aphid collecting honeydew which she stores in her abdomen until it's full; then, she returns to the nest and regurgitates to feed other members of the colony.
Ants, in return for the honeydew, protect the aphids from predators such as flies, wasps, and beetles.
The ants, like human ranchers, sometimes move their aphids to richer grazing grounds.
YUMMY!

24. A Little Aphid Ant Humor

25. Mutualism – sea slug with algae
The algae
lives in the
sea slug
and makes
food for
both of
them – in
return it
gets a place
to live.

26. Nitrogen fixing nodules
Bacteria in the
nodules can take
nitrogen gas from
the atmosphere
and turn it into a
form that can be
used by the plant;
in return, the plant
protects the
bacteria from
harmful oxygen and
the bacteria get
food from the plant.

27. Mutualism - pollination
Many plants depend on
pollinators for their
reproduction. They
provide nectar to attract
these pollinators. So
the pollinator gets fed
and the plant gets
reproduced!

28. Another Pollinator – note pollen on back legs

29. Protozoans in cow’s stomach
These protozoans along with
bacteria help the cow by
digesting cellulose; cows
don’t have the enzymes to
do this.
The protozoans and bacteria get a place to live and a continual food source. This is a valuable mutualistic relationship.

30. OxPecker - Mutualism The oxpecker eats parasites on the mammal –
food for
the bird
and
removal of
danger
for the
mammal

31. Caterpillar Ant Mutualism

32. Commensalism
Commensalism is a relationship where one organism benefits and other is neither harmed nor benefited.
Few examples of commensalism exist because of the difficulty of showing that one of the organisms is not affected by the other. Some of the former commensalistic relationships may turn out to be mutualism or parasitism.

33. Cattle Egret - Commensalism
The cattle stir up
grasshoppers
and other
insects that the
egret likes to
eat. There is
no apparent
benefit to the
cow.

34. Commensalism – shark and remora
The remora
benefits by
getting food
from the
shark’s meal.
But there is no
apparent
benefit to the
shark.

35. Remora without its shark
Note the sucker on the head of the remora (or suckerfish)

36. Commensalism – whale and barnacle
The barnacle larvae swim around, attach to the whale, and form the adult. This habitat is a good one for providing food. The whale does not “appear” to be harmed.

37. Commensalism – limpets on mussel shell

38. Parasitism
Parasitism is a relationship where one individual benefits and the other is harmed. Parasites rarely kill their hosts because to do so would ultimately harm the parasite!
Parasite – benefitted
Host – harmed
A tick!

39. Parasitism Adult wasps insert their eggs beneath the skin of the
hornworm larva.
The eggs hatch and
the young feed
hornworm until they
pupate as shown in
the photo. Although
the parasite is
harmful to the worm,
it is important in
controlling
hornworms in
agriculture.

40. Brood Parasitism - Cowbirds
females lay
their eggs (one
per nest) in the
nests of other
species. The
hatchling
cowbird
is big and gets
most of the
food.
This is because the foster birds tend to feed the largest mouth. The cowbird benefits and the other species is harmed.

41. Mistletoe – a plant parasite
Mistletoe lives off the branches and stems of Other trees. It can photo- synthesize a little but not enough to meet its needs. The tree can be very harmed.

42. Heartworms! The worm larvae are transferred from dog to
dog through the bite of
an infected mosquito.
The mosquito sucks
larval heartworms with
blood from an infected
dog. The mosquito then
bites another dog and
transfers these
microscopic larva as it
bites. During the next few
months, these larva
migrate through the dogs
body arriving at the heart
several months later
where they become
adults.

43. Symbiosis Summary + - Symbiosis Type Species A Species B Commensalism
Mutualism
Parasitism -

44. Ecological Succession
Ecological succession is a process by which an existing ecosystem is gradually replaced by another more stable ecosystem.

45. Primary Succession
Primary succession is succession that occurs on new land.
New land is created by events such as volcanic eruptions or retreat of glaciers that scrape away Earth.
There is no life and no soil present.
The first species that come to the new land are called pioneer species.
These are usually lichens or mosses.
They slowly break down the surface of the rock where they grow and create soil.
Once soil is established, grasses, shrubs, and trees move in from smallest to largest.

46. Secondary Succession
Secondary Succession occurs on land where there was already an ecosystem.
Disturbances such as fire, natural disasters, and clearing occur but leave soil intact.
Succession can occur more quickly because the pioneer species are not necessary.
Herbaceous plants are first to return to the ecosystem, then shrubs and trees quickly return.

47. Climax Community
A climax community is a relatively stable and mature ecosystem.
It is made up of a diverse collection of plants and animals whose niches support a healthy ecosystem.
If an ecosystem is disturbed (by fire, for ex.) ecological succession will proceed toward a climax community