Post on 19-May-2020
An ecosystem includes all living and nonliving factors.
• Abiotic Factors are the nonliving factors that shape an ecosystem
• Examples:
• Soil
• Water
• Sunlight
• Space
• Wind
• Biotic factors are the living factors in the community
• Examples:
• Birds
• Mushrooms
• Trees
• Bacteria
• Grass
• Turtles
• The biotic and abiotic factors together determine:
– the survival and growth of an organism
– the productivity of the ecosystem in which the organism lives
• Together these factors determine if an ecosystem is a suitable habitat for an organism
• What is a habitat? – The area in which the organism lives
(includes the biotic and abiotic factors) – i.e. its “address”
• What is a niche? – The functional role of a species in its community – Not just “where it lives!” – What it does, what it eats, who it eats, how much
and type of resources it uses, how much and type of waste it produces, what its parasites are, etc.
Habitat • A gopher tortoise
needs pine flatwoods with sandy soil
Niche • A gopher tortoise
eats herbaceous plants and creates homes in which other organisms live in
Terminology Review • Habitat: physical environment that surrounds,
influences, and is utilized by a population • Niche: the place where an organism lives and the roles
that it plays in its habitat • Ecological Dominants: the few species that are most
abundant in an ecosystem
Biodiversity Degree of variation of life forms
within an ecosystem Indicator of the health of an
ecosystem (greater biodiversity = better health)
Keystone Species Plays a critical role in maintaining the structure of an
ecological community Not usually the most abundant species in an ecosystem Impact on the community is much greater than would
be expected based on its relative abundance Decline in population causes dramatic changes in the
ecosystem (domino effect) Example: Wolves Sea otters
Sea otters hunted to near
extinction
Sea urchin population
exploded due to lack of predation
from otters
Kelp forests decimated due
to excessive numbers of sea
urchins
Decline in local fish populations
due to loss of habitat
KEYSTONE SPECIES
• Could two squirrel species share the same: – Food supply – Nesting site – Time of day they feed – Habitat
• No two species can share the same niche in the same habitat. (They can have similar niches but not the same.)
• When this occurs there will be competition.
• Competition occurs when organisms (the same or different species) attempt to use the same resource at the same time and in the same place.
• What is a resource? – Any necessity of life – Examples:
• Food • Water • Territory
• Species will evolve to either: – Avoid each other – Tolerate the presence of each other – Aggressively exclude the other
The lion is competing with the vulture for the carcass.
The plants are all competing for space, water, sunlight, and
nutrients.
• No two species can occupy the same niche in the same community at the same time.
• If this occurs they will compete until there is a winner and a loser.
• One species succeed and the other will die (local extinction), migrate, or adapt.
• Leads to Resource Partitioning.
Resource Partitioning “Peace treaties” Differentiation of niches to allow similar
species to coexist in a community Temporal – competition is eliminated by
utilizing the same resource at different times
Spatial – competing species use the same resource by occupying different areas or habitats within the range of occurrence of the resource
Bay-breasted
Warbler
Old needles and bare
and lichen-covered
middle branches
Cape May
Warbler
New needles and
buds at top of tree
Blackburnian
Warbler
New needles and buds
of upper branches
Yellow-rumped
Warbler
Bare or lichen-covered lower
trunk and middle branches
Black-throated
Green Warbler
New needles and
buds and some
older needles
• Occur between individuals of DIFFERENT species
• Symbols: – “+” = a species benefits – “-” = a species is harmed – “0” = a species is not affected
• Competition: - /- • Predation/Herbivory : +/ - • Symbiosis:
– Parasitism: +/- – Commensalism: +/0 – Mutualism: +/+
Predation
o The pursuit, capture, and killing of animals for food
o Predator – an organism that kills and eats another organism
o Prey – an animal that is hunted as a food source for another animal
o Cannibalism – individuals of the same species prey on one another
PREDATION
Modes of Predation • Pursuit (run, swim, fly, dive) • Ambush
Adaptations Predators Acute senses:
smell, sight, hearing
Prey Passive – hiding Active – running away
Benefits of Predation Eliminates sick, weak, and aged individuals in prey population Prevents excessive population growth Helps successful adaptations become more dominant Can enhance reproductive success and long-term survival of prey species
PREDATION
Cryptic coloration Camouflage (blend into background)
PREDATOR/PREY ADAPTATIONS
Aposematic (“warning”) Coloration • Bold coloration serves to draw attention to the prey
animal rather than away from it • Coloration is usually used to advertise the threat that
the animal poses to a predator (usually poison or venom)
PREDATOR/PREY ADAPTATIONS
Mimicry oHarmless
species mimics an unpalatable
or harmful species
PREDATOR/PREY ADAPTATIONS
Other Methods of Protection
Protective or defensive structures Shells Spines
Deceptive behaviors Puffing up or
spreading wings Mimicking a predator
Defensive behaviors Alarm calls Attack “bluffs”
Size limitations (too big to eat)
Chemical Warfare • Irritating • Foul smelling • Bad tasting • Poisonous
PREDATOR/PREY ADAPTATIONS
• Symbiosis = “living together”
• 3 main types:
– Parasitism (+/-): One species benefits at the expense of another
– Commensalism (+/o): rare… One species benefits; the other is not affected
– Mutualism (+/+): Win-win! Both species benefit.
Mutualism • Relationship between two
species in which both derive benefit
• “Partnership” • Examples:
• Rhinos & oxpecker bird • Termites & protists • Mycorrhizae (plant roots
& fungi) • Butterflies and flowers
MUTUALISM
Flowers provide food for insects. Insects spread the seeds of flowers. Both organisms benefit!
Commensalism Relationship between two species in which one benefits and the other is unaffected Examples:
Clownfish & anemones Crab in oyster shell Barnacles on whales
COMMENSALISM
Clownfish hide in poisonous sea anemones which protect them from larger fish. The clownfish
benefit, and nothing happens to the sea anemones.
PARASITISM
Parasitism o Relationship between two
species in which the parasite benefits at the expense of the host
o Though always harmed by the relationship, it is often not fatal to the host
oWhen fatal, death of the host is not immediate
o Parasites may be internal or external
Parasitoidism Similar to parasitism in
that the host is not immediately killed
However, relationship is always fatal to the host
Limited primarily to insects (usually involves eggs being laid in/on a host, which is then slowly consumed by the larvae when they hatch)
PARASITISM
Common Ectoparasites Fleas, mosquitoes, flies, etc. Ticks, mites, etc. Common Endoparasites Tapeworms, hookworms, etc. Malaria, Sleeping sickness, etc.
Ticks bite the dog and feed off its blood. This benefits the tick, but harms the dog.
Effect on Species #1
Positive (+) Neutral (0) Negative (-)
Positive (+) Mutualism Commensalism
Predation Herbivory Parasitism
Effe
ct o
n S
pe
cie
s #2
Neutral (0)
Commensalism N/A Competition
Negative (-)
Predation Herbivory Parasitism
Competition Competition
Ecological Succession oNatural, gradual changes in the types of species that
live in an area
Pioneer Species Characteristics: Short-lived &
reproduce frequently Numbers can be great Tolerate lack of
moisture & extreme temperatures
Involved in soil formation
Often secrete chemicals that break down rocks
Stabilizing nutrient cycle
Examples: Lichens Mosses Weeds Grasses
Ecological Succession oNatural, gradual changes in the types of species that
live in an area
Ecosystem Structure During Early Successional Stage
• Plant size – small • Species diversity – low • Trophic structure – mostly
producers, few decomposers • Ecological niches – few, mostly
generalized • Community organization - low
Primary Succession Begins in a place
without any soil Starts with the arrival
of living things that do not need soil to survive (Pioneer Species)
Examples: Glaciers Volcanic eruptions Asteroid impacts
Primary Succession Process 1. Soil starts to form as lichens and the forces of weather
and erosion help break down rocks into smaller pieces. 2. When lichens die, they decompose, adding small
amounts of organic matter to the rock to make soil. 3. Simple plants like mosses and ferns can grow in the new
soil. 4. The simple plants die, adding more organic material. 5. The soil layer thickens, and grasses, wildflowers, and
other plants begin to take over. 6. These plants die, and they add more nutrients to the soil. 7. Shrubs and tress can survive now. 8. Insects, small birds, and mammals have begun to move
in. 9. What was once bare rock now supports a variety of life.
• Mosses and lichens create soils in this example of primary succession from Yosemite National Park, CA.
• The valley emerged ~10,000 years ago after being scraped clean by a glacier
• Grasses, shrubs and even trees appear where soil has slowly developed.
Secondary Succession
• Begins in a place that already has soil and was once the home of living organisms
• Occurs faster and may have different pioneer species than primary succession
• Examples: – Fires – Hurricanes – Earthquakes
Yosemite National Park, CA.
After a wildfire, grasses and tree seedlings grow up to replace the burned forest.
Yosemite National Park, CA.
Longer after a wildfire, shrubs and short trees grow up to replace the burned forest. A few gray snags of the
old burned forest are still visible.
Climax Communities Climax community – a stable group of plants and
animals that is the end result of the succession process
Characteristics: Complex food webs dominated by decomposers Well-established, efficient nutrient cycles High occurrence of vegetative patches Low immigration/emigration rate Many, specialized niches Efficient use of energy High species diversity Contain large plants High biomass
Potential Disturbances o Some disturbances that
may disrupt a stable climax community: oDrought o Fire o Flooding oMining o Clear-cutting a forest o Plowing a grassland oApplying pesticides o Climate change o Invasion of exotic
species
Yellowstone Park forest fire, 1988
• Disturbances can be GOOD for the ecosystem! • The majority of Florida is made up of pine forests. • Pine trees need lots of light. • Disturbances will kill off competing vegetation
and allow pine trees to reproduce. • Prescribed (intentional and controlled) fires:
– Help prevent wildfires – Promotes biodiversity – Kills pests (ticks, etc)
• REMEMBER: Fire is a natural part of our ecosystem!