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14.1 Habitat vs. Niche
Habitat – all biotic and abiotic factors where an organism lives
– WHERE a species lives
2
Ecological Niche
All physical, chemical, and biological factors needed to:
– Stay alive
– Stay healthy
– Reproduce
3
Ecological Niche
Can be described in terms of:
– Space utilization
– Food consumption
– Where it fits in the food web
– When it’s active
– Temperature range
– Moisture requirements
– Mating requirements
4
Ecological Niche
Role of particular species in ecosystem – Its “job”
The impact of its presence
How an organism lives within its habitat
NOT WHERE it lives 5
Resources to Survive
Organisms must have:
– Food
– Shelter
– Water
Birds of Paradise
5 min
6
Competition
When two species must use same resources
– Food
– Living space
– Light
– Water
– Mates
7
Competitive Exclusion
If two species are competing, the one that uses the resource(s) most efficiently will eventually eliminate the other
– One eliminated:
New niche
Become extinct
8
Niche Partitioning
When a niche is divided
– Animals stay in only part of area even though they could live in any of it
– Avoids competition
Ex: Bees and butterflies Both use flowers for food
9
Ecological Equivalents
Species that occupy similar niches but live in different areas
– Ex: Poison dart frog of South America and mantella frog of Madagascar
– Both:
Bright, poisonous, live in similar habitats, eat similar insects
DON’T compete bc live in different areas of world
11
14.2 Community Interactions
Competition Two species use same resources
Predation – one organism captures and feeds on another
12
Competition
1) interspecific – between 2 different species
– Ex: dandelions and grass
2) intraspecific – within same species
– Ex: male birds
14
Symbiotic Relationships
Symbiosis
– Different organisms living in close, long term relationship
Types:
– Mutualism
– Commensalism
– Parasitism
15
Mutualism
Both benefit
Animal partnerships 4:20
16
Mutualism
Ex: Ants and aphids
– Aphids suck fluid (honeydew) from plants
– Ants “milk” aphids; use honeydew as food
– Ants protect aphids
17
Commensalism
One benefits , one unaffected
Ex:
– Demodicids (mites) in eyelashes
– The Unknown Micro World 7 min
18
Commensalism
Ex:
– Sea anemone
Tentacles are poisonous
– Clown fish
Protection; not bothered by poison
19
Parasitism
2 types:
– Ectoparasite – live on outside of host
Ex: leeches, ticks, fleas
– Endoparasite – lives on inside of host
Ex: tapeworms, hookworms
22
14.3 Population Density
Number of individuals in a defined space
= # of individuals
area (units2)
23
Population Dispersion
How individuals within a population are spread in an area
3 types:
– 1) clumped
– 2) uniform
– 3) random
24
Survivorship Curve
Diagram that shows # of survivors of a group over time
Ex: All the people born in 1920
– Track until all die
– Plot data
3 Types:
– I
– II
– III
28
Type III
High birth rate and infant mortality rate
– Few survive until adulthood
Ex:
– Invertebrates
– Fish
– Amphibians
– Plants
31
14.4 Demography
Statistical study of populations
Demographer
– Studies composition of a population
– Predicts changes in size
32
Population Changes
Immigration – individuals move into an area
Emigration – individuals move out of an area
Birth
Death 36
Population Growth Curves Graph – Change in population over time
Y-axis = Population
X-axis = Time (generations)
37
Exponential Growth
Population increases dramatically in short time – Resembles “J”
shape
– Ex: rabbits in Australia 24 brought for sport
hunting
Now over 200 million
Australian Rabbits 2:46 38
Carrying Capacity
Max population an environment can support
– Cannot grow unchecked
Limited by:
– Predators
– Disease
– Resources
– Population density
39
Logistic Growth
Population held in check: – Resembles “S”
shape
– Carrying capacity represented
Takes into account declining resources
How most populations grow
40
Logistic Growth
Carrying Capacity:
– If Below
rate is rapid
– If Near
rate slows
– If above
rate falls
41
Population Crash
Dramatic decline in short time
Ex. of Causes:
– Food
– Disease
– War
Ex: Reindeer on St. Matthew Island, AK
42
Limiting Factor
Factor w greatest effect of keeping population down
2 types:
– Density-dependent
– Density-independent
43
Invasive Species
Do not belong
– Not native
– Exotics
– Have not developed relationships over long periods of time
Problems!
44
Density-dependent
Affected by # of individuals in area
– More crowded can lead to more problems
Ex:
– Competition
– Predation
– Parasitism
– Disease 45
Density-independent
Parts that limit population growth regardless of population density
Ex:
– Unusual weather
– Natural disasters
– Human activities
46
14.5 Succession
Sequence of biotic changes
– Regenerate damaged community
– Creates new community in a previously uninhabited area Ex: Hawaii
– Regular progression of species replacement
47
Primary Succession
Pioneer Species
– First organisms to live in a previously uninhabited area
“Colonizers”
– Small fast growing plants
– Change the soil over time
Ex: lichens and some mosses
50
Secondary Succession
Reestablishment of a damaged ecosystem where soil was left intact – Ex: abandoned field
or forest clearing
Always occurring
51
Example of Succession
Glacier Bay, Alaska
Primary succession
– Receding glacier left piles of rocks and gravel
– Pioneer species
Lichens
Moss
Fireweed
Willows
52
Glacier Bay Succession
10 years later
– Dead leaves of plants enriched soil
– Alders enter by seed
Nitrogen fixing nodules add nitrogen to the soil
53
Glacier Bay Succession
30 years later:
– Willows
– Alders
– Cottonwoods
– Thickets of trees and shrubs
Kill smaller pioneer species
54