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Unit 3 Ecology
SB4. Students will assess the dependence of all organisms on one another and the flow of energy and matter within their ecosystem.
a. Investigate relationships among organisms, populations, communities, ecosystems, and biomes.
LEQ1: What relationships exist among organisms,
populations, communities, ecosystems, and biomes?
Relationships
• Ecology is the study of relationships among organisms and their environment.– Interactions between living things and their
environment– Interactions among living things
• Ecologists study the environments different levels of organization.– Organism– Population– Community– Ecosystem– Biome– Biosphere
Relationships
• An organism is an individual living thing, such as an alligator.– Species: group of similar organisms that can breed
and produce fertile offspring.
Relationships
OrganismOrganism
• A population is a group of the same species that lives in one area.
Relationships
Organism
PopulationPopulation
Organism
• A community is a group of different species that live together in one area
Relationships
Organism
Community
Population
Community
Population
Organism
• An ecosystem includes all of the organisms as well as the climate, soil, rocks, water, and other nonliving things in a given area.
Relationships
Organism
Population
Community
Ecosystem Ecosystem
Organism
Population
Community
• A biome is a major regional or global community if organisms characterized by the climate conditions and plant communities that thrive there.
Relationships
Community
Population
Ecosystem
Community
Population
Organism
Organism
Biome
Ecosystem
• The biosphere contains the combined portions of the planet in which all of life exists.– All biomes (land, water, air)– The entire planet
Relationships
Biosphere
Biome
Ecosystem
Community
Ecosystem
Community
Population
Organism
Population
Organism
Ecologist Study Relationships
• Observation– Direct Survey
• Used for easy to spot species
– Indirect Survey• Used for species that are
difficult to spot or track• Look for signs of their
presence.
Relationships
• Experimentation– Conducted in lab which
gives researchers more control
– Conducted in the field which is a more accurate account of natural interactions
Relationships• Modeling
– Allows scientists to learn about organisms or ecosystems in ways that would not be possible in a lab or natural setting
• Use computer and mathematical models
Ecologists use data transmitted by GPS receivers worn by
elephants to develop computer models of the animal’s
movements.
Biotic and Abiotic Factors
• Every ecosystem includes both living and nonliving factors
• Biotic factors are living things.– Plants– Animals– Fungi– Bacteria
Biotic and Abiotic Factors
Plants
• Abiotic factors are nonliving things– Moisture– Temperature– Wind– Sunlight– soil
Biotic and Abiotic Factors
Sunlight
Moisture
• Changing one factor is an ecosystem can affect many other factors– Biodiversity is the assortment, or variety, of
living things in an ecosystem.– Rain forests have more biodiversity than other
locations in the world, but are threatened by human activities
Biotic and Abiotic Factors
• A keystone species is a species that has an unusually large effect on its ecosystem.– They form and maintain a complex web of life
Biotic and Abiotic Factors
keystone
Biotic and Abiotic Factors
creation ofwetland
ecosystem
increased waterfowlPopulation
increased fishpopulation nesting sites
for birds
keystone species
• Every organism has a habitat and a niche.
Habitat and Niche
• A habitat differs from a niche.
• A habitat is all aspects of the area in which an organism lives– Biotic factors– Abiotic factors
• Your address
Habitat and Niche
• An ecological niche includes all of the factors that a species needs to survive, stay healthy, and reproduce– Food – Abiotic conditions– Behavior
• Your occupation
Habitat and Niche
• Species can share habitats but cannot occupy the same niche in the same ecosystem.
• Competition occurs when two species use resources in the same way (occupy same niche)
• Competitive exclusion keeps two species from occupying the same niche.
Habitat and Niche
Habitat and Niche
Competitive exclusion has three different outcomes:
1. One species is better suited to the niche and the other will either be pushed out or become extinct.
2. The niche will be divided.
3. The two species will further diverge.
Habitat and Niche• Ecological equivalents are species that
occupy similar niches but live in different geographical regions.Madagascar
South America
Community Interactions
• Organisms interact as individuals and as populations
• There are three main ways in which organisms interact:– Competition– Predation– Symbiosis
• Mutualism• Commensalism• Parasitism
Community Interactions
Community Interactions
• Resource availability gives structure to a community.• Competition occurs when two organisms fight for the
same limited resource.
Types of competition:• Intraspecific• Interspecific
• Predation occurs when one organism captures and eats another organism.
Community Interactions
Predator
Prey
• Symbiosis is a relationship in which two species live closely.
• Three types:– Mutualism– Commensalism– Parasitism
Community Interactions
• Mutualism: both organisms benefit
Community Interactions
• Commensalism: one organisms benefits, the other is unharmed.
Community Interactions
Human: Our eyelashes
are home to tiny mites
that feast on oil secretions and
dead skin. Without harming
us, up to 20 mites may be living in one
eyelash follicle.
Demodicids Eyelash mites find all they need to survive in the tiny follicles
of eyelashes. Magnified here 225
times, these creatures measure
0.4 mm in length and can be seen only with
a microscope.
• Parasitism: one organism benefits, the other is harmed.
Community Interactions
Hornworm caterpillarThe host
hornworm will eventually die as
its organs are consumed
by wasp larvae.
Braconid waspBraconid larvae
feed on their host and release
themselves shortly before
reachingthe pupae stage of development.
Community Interactions
Endoparasites
Hookworms
Extoparasites
Leeches
Endoparasites• Live in tissue and organs of
organism• Feed on nutrients ingested by host• Examples: tapeworms, protozoan,
hookworms
Extoparasites• Exterior of organism• Feed on host fluids• Example: leeches, fleas, ticks
Population Density And Distribution
• Each population has a density, a dispersion, and a reproductive strategy.
• Population density is the number of individuals that live in a defined area.– a measurement of the number of individuals
living in a defined space.
• Scientists can calculate population density.
Population Density And Distribution
• Geographic dispersion of a population shows how individuals in a population are spaced.– Population dispersion refers to
how a population is spread in an area.
• There are three types of dispersion:– Clumped– Uniform– Random
Population Density And Distribution
Clumpeddispersion
Uniformdispersion
Randomdispersion
Clumped
Population Density And Distribution
Uniform
Population Density And Distribution
Random
Population Density And Distribution
• Survivorship curves help to describe the reproductive strategy of a species.– Diagram showing the number of surviving members
over time from a measured set of births.
Population Density And Distribution
• Survivorship curves can be type I, II or III• Type I -low level of infant mortality and an older
population– Common to large mammals and humans
• Type II -survivorship rate is equal at all stages of life– Common to birds and reptiles
• Type III -very high birth rate, very high infant mortality.– Common to invertebrates and plants
Population Density And Distribution
Population Density And Distribution
Population and Growth Patterns
• Populations grow in predictable patterns
• The size of a population is always changing.
• Four factors affect the size of a population:– Immigration:
• organisms coming into a ecosystem
– Births– Emigration
• Organisms leaving an ecosystem
– Deaths
Population and Growth Patterns
• Population growth is based on available resources.
• There are two types of growth:– Exponential – Logistic
Population and Growth Patterns
• Exponential growth is a rapid population increase due to an abundance of resources.
Population and Growth Patterns
• Logistic growth is due to a population facing limited resources.– Population will level out around carrying
capacity.
Population and Growth Patterns
• Carrying capacity is the maximum number of individuals in a population that the environment can support.
• A population crash is a dramatic decline in the size of a population over a short period of time.
Population and Growth Patterns
Population and Growth Patterns
• Ecological factors limit population growth.
• A limiting factor is something that keeps the size of a population down.
• There are two types of limiting factors:– Density dependent– Density Independent
Population and Growth Patterns
• Density dependent limiting factors are affected by the number of individuals in a given area.
• Examples: – Predation– Competition– Parasitism and
disease
Population and Growth Patterns
• Density independent limiting factors limit a population’s growth regardless of the density.
• Examples:– Unusual weather– Natural disasters– human activities