2.1 and 8 Community Ecology new revision slides

1. Community Ecology
IB: 2.1
Ch. 8
Videos – extinction clip on exotics, clip
on coral reefs

2. 2.1 Species and Populations
• A species is a group of organisms that share common
characteristics and that interbreed to produce fertile offspring.
• A habitat is the environment in which a species normally lives.
• A niche describes the particular set of abiotic and biotic
conditions and resources to which an organism or population
responds.
• The fundamental niche describes the full range of conditions
and resources in which a species could survive and reproduce.
The realized niche describes the actual conditions and
resources in which a species exists due to biotic interactions.

3. • The interactions between the organisms—such
as predation, herbivory, parasitism, mutualism,
disease, and competition—are termed biotic
factors.
• • Interactions should be understood in terms of
the influences each species has on the
population dynamics of others, and upon the
carrying capacity of the others’ environment.

4. Vocabulary
• Community
• Competition
• Mutualism
• Niche
• Parasitism

6. Definitions
1. Population  a group of individuals of a certain
species in a given area at a given time: blue crabs in
the Halifax river
2. Community  interacting groups of populations in an
area: the scrub community on campus
3. Species  a group of individuals who can interbreed
to produce fertile, viable offspring: FL panthers
4. Niche  The role of an organism in its environment
(multidimensional): nocturnal predator of small
mammals in the forest
5. Habitat  Where an organism typically lives:
mangrove swamps

7. Community Structure
• Consider the spatial distribution of
organisms
• Physical appearance: Size, stratification,
distribution of populations and species
• Species diversity and richness: number of
different species
• Species abundance: number of individuals
of each species
• Niche structure: number, uniqueness and
interaction of niches available

8. m
ft
10
50
20
30
100
Tropical
rain forest
Coniferous
forest
Deciduous
forest
Thorn
forest
Tall-grass
prairie
Short-grass
prairie
Desert
scrub
Thorn
scrub
Comparison of types, sizes and stratification of species
in different terrestrial communities (complexity)

9. Community Differences
• Aquatic systems  deep ocean, sandy beach,
lakes, rivers, wetlands
• Physical structure varies
– Most habitats are mosaics, vegetation patches
– Sharp edges or broad ecotones (transition zones)
– Physical properties differ at edges = edge effect
– Forest edge may be sunnier, drier, warmer
• different species at the edge
• Many wild game species found here
• Edges can fragment habitat  vulnerability & barriers

12. What is a niche
• The organisms role in its environment
• How it responds to the distribution of
resources
• Many dimensions to it – therefore an n-
dimensional hypervolume
• No two species can occupy the same
niche for any period of time
• If a niche is vacant organisms will quickly
adapt to fill it

13. • Fundamental Niche  Everything that the
organism could possibly do given a
competitor free environment
• Realized Niche  Everything the
organism does after competition limits
them

14. Connell’s
Barnacles

15. Biodiverse Communities
• Top species rich environments are tropical
rainforests, coral reefs, deep sea, large
tropical lakes
• Usually high diversity but low abundance
• Factors for increased diversity
1. Latitude: most diverse near equator
2. Depth: marine communities peak about 2000m
3. Pollution: more pollution  less species
On land increases in solar radiation, precipitation,
seasonal variation, decreased elevation

16. Species
Diversity
Species
Diversity
1,000
100
10
Latitude
80ºN 60 40 20 0
200
100
0
90ºN 60 30 0 30ºS 60
Latitude
Effects of Latitude

17. Species
diversity
25
20
15
5
10
0
0 2,000 4,000 6,000
Depth (meters)
0 2,000 4,000 6,000
Depth (meters)
25
20
15
5
10
0
Coast Deep Sea Coast Deep Sea
Snails Tube worms
© 2004 Brooks/Cole – Thomson Learning
Effects of Depth

18. Number of individuals per diatom species
Number
of
diatom
species
Unpolluted
stream
Polluted
stream

19. The Island Effect
• Isolated ecosystems studied by MacArthur
and Wilson in 1960’s
• Diversity effected by island size & degree
of isolation
• Island Biogeography theory: diversity
effected by
– Rate of species immigration to island
– Rate of extinction on island
– Equilibrium point = species diversity

20. High
Low
Rate
of
immigration
or
extinction
Equilibrium number
Immigration and extinction rates
Number of species on island
(a)
© 2004 Brooks/Cole – Thomson Learning

21. Island Biogeography
• Immigration and Extinction Effected by
1. Size:
– small island has less immigration (small target),
– Small island has fewer resources, more extinction
2. Distance from mainland:
– Closer to mainland  more chance of immigration
• Applied in conservation for “habitat islands”
like national parks surrounded by
development

22. High
Low
Rate
of
immigration
or
extinction
Small island
Effect of island size
Number of species on island
(b)
Large island
© 2004 Brooks/Cole – Thomson Learning

23. Island Biogeography Data
• South Pacific
Islands study
looked at bird
diversity as
distance from
New Guinea
increased
• Caribbean Island
study found
bigger islands
had more species
diversity than
smaller islands
which were
otherwise similar
100
50
25
12.5
6.25
0 2,000 4,000 6,000 8,00010,000
Distance from New Guinea (kilometers)
Number
of
species
(percentage
of
sample
studied
)
NEW GUINEA
100
1 10 100 1,000 10,000 100,000
Area (square miles)
Number
of
amphibian
and
reptile
species
10
SABAMONTSERRAT CUBA
Hispaniola
Puerto Rico
Jamaica
Cuba
Montserrat
Saba
Redonda
©
2004
Brooks/Cole
–
Thomson
Learning

24. Communities have different
“Types” of Species
• Native species = species that normally live
and thrive in a particular community
• Nonnative species = species that are
accidentally introduced into an area
• Keystone species = species that are more
important than their abundance or
biomass suggest
• Indicator species = species that serve as
early warnings of damage in a community

25. Nonnative Species
• Also called exotics, aliens, or introduced sp.
• FL examples include fire ants, hydrilla, potato
vine, peacock bass, …
– Occupy niches excluding native organisms
– Reproduce rapidly in absence of natural
predators
– Usually are very adaptable to human disturbed
environments

26. Common Florida Exotics

27. Indicator Species
• Mostly species that respond quickly to changes
in the environment
• Birds indicate tropical forest destruction
• Trout indicate pollutant presence in water
• Amphibians are a classic indicator
– Frogs case study p 170
– Frog decline and deformities

28. Keystone Species
• Strong interactions with other species
affect the health and survival of those
species
• They process material out of proportion to
their numbers
• Roles include: pollination, seed dispersion,
habitat modification, predation by top
carnivores, efficient recycling of animal
waste

29. Sea Otters

30. Keystone Species II
• Habitat modification
– Elephants – knock over trees in savannah to
promote grass growth & recycle nutrients
– Bats & birds – regenerate deforested areas
by depositing plant seeds in their droppings
– Beavers – create ponds forming habitats for
many pond dwelling species like fish, ducks,
& muskrats

32. Keystone Species III
• Top predators  exert stabilizing effect by
feeding on and regulating certain species
– Wolves, leopards, lions, gators, sharks, otters
• Over 300+ species are found on the wolf kills
made in Yellowstone

34. Wolves
• http://www.wolfquest.org/index.php

35. Waste
removal
•Dung beetles
– remove bury
and recycle
animal waste
•Establish new
plants
•Aerate soil
•Reduce
disease
causing
microorganis
ms

36. Species Interactions
• Interactions may be harmful, beneficial, or
have no effect at all
• Competition: Intraspecific or Interspecific
• Predation, Mutualism (Symbiosis),
Commensalism, Parasitism

37. Intraspecific Competition
• Competition between members of the same
species for a common resource
• Resource: food, space, mates, etc.
• Territoriality
– Organisms patrol or mark an area
– Defend it against others
– Good territories have
• Abundant food, good nesting sites, low predator pop.
– Disadvantage = Energy, Reduce gene pool

38. Territoriality Examples

39. Interspecific Competition
• 2 or more different species involved
• Competing for food, space, sunlight, water,
space, nesting sites or other limited resource
• If resources abundant, they can be shared but in
nature they are always limited
• If fundamental niches overlap  competition
• One of the species must…
1. Migrate if possible
2. Shift feeding habits or behavior = Evolve
3. Suffer a sharp population decline
4. Become extinct

40. Connell’s
Barnacles

41. Methods of competition
1. Interference
• One species limits access of others to a
resource, regardless of its abundance
• Hummingbird territoriality, Desert plant
allelopathy
2. Exploitation
• Species have equal resource access, differ
in speed of use
• Quicker species = more of it & hampers
growth, reproduction and survival of other
species

42. Allelopathy

43. Competitive Exclusion Principle
• One species eliminates another in an area
through competition for limited resources
– Two Paramecium species
– Identical conditions grown apart both do well
– Grown together one eliminates the other
• The niches of two species cannot overlap
significantly for a long period of time

44. High
Low
Relative
population
density
0 2 4 6 8 10 12 14 16 18
Days
Each species grown alone
Paramecium
aurelia
Paramecium
caudatum

45. High
Low
Relative
population
density
0 2 4 6 8 10 12 14 16 18
Days
Both species grown together
Paramecium
aurelia
Paramecium
caudatum

46. Avoiding Competition
• Resource partitioning = dividing of scarce
resources to species at different
– Times
– Methods of use
– Different locations
• Species occupy realized niche, a small
fraction of their fundamental niches
– Lions vs leopards, hawks vs. owls

47. Number
of
individuals
Number
of
individuals
Resource use
Resource use
Species 1 Species 2
Region
of
niche overlap
Species 1 Species 2
© 2004 Brooks/Cole – Thomson Learning

49. Predation
• Members of one species feed directly on all
or part of a living organism of a different
species
• Individuals  predator benefits, prey harmed
• Population  prey benefits: take out the
weak, greater resource access, improved
gene pool
• Predator plays important ecological role

50. Predation

51. Predation strategies
1. Herbivores – sessile prey, no need to
hurry
2. Pursuit – speed (cheetah), eyesight
(eagles), cooperation (wolves)
3. Ambush – camouflage for hiding (praying
mantis), lures (anglerfish)

52. Ambush Predators

53. Prey defenses
• Camouflage – change color, blend with
environment,
• Chemical warfare – produce chemicals which
are poisonous, irritating, bad smelling or
tasting
• Warning coloration – bright colors advertise
inedibility (mimics take advantage of this)
• Behavioral strategies – Puffing up, mimicking
predators, playing dead, schooling

54. Warning coloration

55. Batesian mimicry

56. Mullerian mimicry

57. Span worm Bombardier beetle
Viceroy butterfly mimics
monarch butterfly
Foul-tasting monarch
butterfly
Poison dart frog When touched, the
snake caterpillar
changes shape to look
like the head of a snake
Wandering leaf insect
Hind wings of io moth
resemble eyes of a
much larger animal

58. Parasitism
• One species feeds on part of another
organism (the host) without killing it
• Specialized form of predation
• Parasite Characteristics
1. Usually smaller than the host
2. Closely associated with host
3. Draws nourishment from & slowly weakens host
4. Rarely kills the host
• Examples = Tapeworms, ticks, fleas, fungi

59. Parasites

60. Malaria
According to the World Health
Organization there are 300 to 500
million clinical cases of malaria
each year resulting in 1.5 to 2.7
million deaths
The disease kills more than one
million children - 2,800 per day -
each year in Africa alone. In
regions of intense transmission,
40% of toddlers may die of acute
malaria.
In the early 1960s, only 10% the
world's population was at risk of
contracting malaria. This rose to
40% as mosquitoes developed
resistance to pesticides and
malaria parasites developed
resistance to treatment drugs.
Malaria is now spreading to areas
previously free of the disease.

61. Mutualism
• Symbiotic relationship where both species
benefit
• Pollination, Nutrition, Protection are main
benefits
• Not really cooperation, both benefit by
exploiting the other

62. Mutualism II
Examples
1. Lichens – fungi & algae living together
 food for one, structure for the other
2. Plants and Rhizobium bacteria  one
gets sugars the other gets nitrogen
3. Oxpeckers and Rhinos  food for one,
less parasites for the other
4. Protists and termites  break down
wood for one, nutrients for the other

63. Oxpeckers and black rhinoceros
Clown fish and sea anemone

64. Human Intestinal Symbionts

65. Commensalism
• One species benefits
the other is neither
harmed nor helped
– Examples
1. Herbs growing in the
shade of trees
2. Birds building nests in
trees
3. Epiphytes = “Air plants”
which attach
themselves to the trunk
or branches of trees
-they have a solid base to
grow on and better
access to sunlight & rain

67. What interaction is this?

68. What interaction is this?

69. What interaction is this?