Predator/Prey Relationships

Ecology

What Is Ecology?

• Study of the interactions that take place between an organism and its environment

• Abiotic factors: nonliving parts of

environment, ex. light, temperature, weather, etc.

• Biotic factors: living parts of environment, ex.

relationships between and among organisms

Levels of Organization

• Organism

• Species

• Population

• Community

• Ecosystem

• Biome

• Biosphere

• Species: a group of similar individuals that can interbreed and produce

fertile offspring

– Ex. the Eastern cottontail rabbit species

• Population: a group of the same

species that can interbreed, produce fertile offspring, and live in the same place at the same time

– Ex. the cottontails living on my street

• Community: a group of interacting populations in the same place at the same time

– Ex. ALL of the cottontails, squirrels,

chipmunks, and birds living on my street

• Ecosystem: interacting communities; includes biotic and abiotic factors

– Ex. all of the cottontails, squirrels, chipmunks, and birds living on my street, plus the weather

Niche vs. Habitat

• Niche: strategies and adaptations a species uses in its environment

– HOW the organism lives; its “job”

– How it gets its food and shelter, how it survives, how it reproduces, etc.

• Habitat: WHERE an organism lives its life

Predator/Prey Relationships

• Predator = organism that “does the eating”

• Prey = organism that gets eaten Predator/prey simulation: http://

phet.colorado.edu/en/simulation/natural-select ion

Symbiotic/Survival Relationships

• Symbiosis: close and permanent

association between organisms of a different species

• Helps maintain survival

1) Mutualism: both species benefit

Ex. 1: ants and acacia trees in jungles

Ex. 2: “cleaner” fish ^http://

www.youtube.com/watch?v=Sp6d-56npwo&safe=active

2) Commensalism: one species benefits and the other is neither harmed nor benefited

Ex. Spanish moss on trees

3) Parasitism: one species benefits, the other species is harmed

Ex. ticks on a dog

*Parasites usually do not kill their hosts because the parasite would also die

• Note: predator-prey relationships are NOT symbiotic relationships because they are not long-term!

Coevolution

• When organisms evolve in response to each other

• Ex: rabbit and fox populations being able to run faster and faster with each successive generation

Energy Movement

• Organisms obtain energy by being one of the following:

1) Autotroph: organism uses light energy or chemical energy to make its own food

-Also known as a producer

2) Heterotroph: organism cannot make its own food and must feed on other organisms

-Also known as a consumer

Types of Heterotrophs

• Herbivore: eats only plants, ex. rabbits and cows

• Carnivore: eats only other animals, ex. lions and tigers

• Omnivore: eats both plants and animals, ex. raccoons and bears

• Scavenger: eats dead animals, ex. hyenas and vultures

• Decomposer: breaks down dead and decaying plants and animals, ex. fungi and bacteria

• Note: you can usually tell what type of heterotroph an organism is based on its skull

Energy Flow

• Food chain: simple model that shows how matter and energy move through an

ecosystem

• Direction of the arrows shows the direction of energy movement, NOT who eats whom!

• After each transfer of energy from one

organism to the next, a portion of that energy is lost due to heat

Trophic Levels

• Trophic level: “feeding step” in a food chain -1^st trophic level is made of producers

-1^st order trophic level is made of herbivores (aka

“primary consumers”)

-2^nd order trophic level is made of carnivores (aka

“secondary consumers”)

-3^rd order trophic level is made of carnivores and other consumers (aka “tertiary consumers”)

Food Webs

• Food web: more complex model that shows all possible feeding relationships between

organisms in an ecosystem

• Essentially a network of interconnected food chains

• More realistic because most organisms

depend on more than one organism for food

Ecological Pyramids

• Pyramid of energy:

shows energy

movement up the food chain

• The most energy is at the producer level

• 90% of energy is lost at each level as you move up the pyramid

• Pyramid of numbers: shows how many

organisms are needed to support the food chain

• Producers are the most numerous

• Pyramid of

biomass: shows how much

biomass is found at each trophic level

• Producers are the most numerous and have the

greatest total mass

Biological Magnification

• The buildup of toxins at upper trophic levels

Cycles in Nature

• Water cycle = movement of water from the air to the ground and back to the air

• Carbon cycle = carbon is passed between carbon

dioxide in the air and organic molecules in living things

– Cell respiration = C₆H₁₂O₆ + 6O₂  6CO₂ + 6H₂O

– Photosynthesis = 6CO₂ + 6H₂O + light energy  C₆H₁₂O₆ + 6O₂

• Nitrogen cycle = nitrogen gas in the atmosphere is

converted into nitrates and nitrites for organisms to use

Mr. Anderson’s cycles podcast (start at 4:30): http://

www.youtube.com/watch?v=09_sWPxQymA

Succession

• Succession: orderly, natural changes and species replacements that take place in a community or ecosystem

Primary Succession

• Colonization of barren land by communities

• Takes place on land where there are no living organisms

• Pioneer species: first species to take hold in a once-barren area of land

-Ex. lichens and mosses

http://www.mrphome.net/mrp/succession.swf

Secondary Succession

• Changes that take place after an existing community is severely disrupted

• The community of organisms gradually changes

• Over time, both primary and secondary succession will reach a “climax community” that is relatively stable

• Mr. Anderson’s Succession podcast: http://

www.youtube.com/watch?v=V49IovRSJDs http://ecoplexity.org/node/219

Exponential Growth

• Shown on a graph by a J-shaped curve

• Initial growth is slow but once organisms start reproducing, the population increases rapidly and grows at a faster rate

• Carrying capacity: when a population grows so large that its habitat can no longer support it (shown by K on a graph)

• Limiting factor: any biotic or abiotic factor that limits or restricts a population

• Density dependent factors: effects depend on how dense the population is; become more intense as the population density increases

• Density independent factors: occur independently of populations

Dependent or Independent?

• Blizzard

• Buildup of toxic waste

• Competition

• Disease

• Earthquake

• Fire

• Lack of space

• Predation

Logistic or Restricted Growth

• Shown on a graph by an S-shaped curve

• Limiting factors have come into play and

the population begins to stabilize

• Carrying capacity has been reached and is shown by a dotted line

Growth Rate

r = births-deaths

N

• r = reproductive or growth rate

• N = population size at the beginning of the time interval when births and deaths are counted

Life History Patterns

• Different growth rates for populations are relative to the carrying capacity of the

environment

• At low population densities, there are many resources available

• This allows organisms to reproduce rapidly and the population rate increases quickly

• When populations have higher densities near the environment’s carrying capacity, fewer

resources are available

• Selection favors adaptations that allow

organisms to survive and reproduce with few resources

r-Selected/Opportunistic Species

• Show rapid, exponential growth (J-shaped curve)

• Found in variable environments where population densities fluctuate

• Produce many offspring that are small, mature quickly, and require little parental care

• Ex. many grass species, rodents, bacteria, and insects

K-selected/Equilibrial Species

• Population size remains relatively constant at the carrying capacity K

• Usually inhabit a stable environment

• Produce a small number of relatively large

offspring that require extensive parental care until they mature

• Ex. elephants, whales, and trees

Human Populations

• Demography: the study of human population size, density and distribution, movement, and birth and death rates

• The human population shows exponential growth and is currently growing at a rate of more than 80 million people per year

• You can calculate a population’s growth rate with the following formula:

r = births-deaths

N

• r = reproductive or growth rate

• N = population size at the beginning of the time interval when births and deaths are counted

• If 60 new babies are born in a year and 10

people die in a population of 1000, its growth rate would be….

60-10/1000 = .05 per year

• The population size is increasing

• If the birth rate of a population is greater than the death rate, is r positive or negative? What does this mean?

• If the birth rate is less than the death rate, what is happening within the population?

• What does it mean if the birth rate equals the

death rate and the population growth rate is zero?

• Mr. Anderson’s Ecosystems podcast (review, start at minute 5:45): http://

www.youtube.com/watch?v=Ot_KmOTYfRA&safe=

active

Human Impact and Biodiversity

• Biodiversity: the variety of species in an area

• The most common measure of biodiversity is the number of different species in an area

• Ex. One acre of farmland that contains only corn (and other organisms such as mice and insects that live in the cornfield) has less biodiversity than one acre of tropical rainforest, which may contain thousands of species

Why Is Biodiversity Important?

• Living things are all interdependent, which means that they all depend on each other

• Animals could not exist without green plants, and many flowering plants depend on animals to pollinate them

• Decomposers break down dead or decaying organisms into nutrients that they can absorb and use

• Populations are adapted to live together in communities

• If one species is lost from an ecosystem, the loss may have consequences for other living things in the area

• Remember your food webs– if one organism was removed, how would that food web

change?

Threats to Biodiversity: HIPPO

• Habitat loss: damage to a habitat by….

• Invasive species: the introduction of non-native (“exotic”) species that compete with (and

sometimes out-compete) native species for food, shelter, light, physical space, etc.

– Sometimes they are introduced purposefully , ex.

kudzu to control erosion

– Sometimes they “escape” or “stow away” by accident, ex. Burmese pythons that invaded the Everglades after people abandon their pets, or brown tree snakes that hid on planes and have taken over Guam

HIPPO, cont.’d

• Pollution

– Air: burning fossil fuels, acid rain, and damage to the ozone layer

– Water: excess fertilizers cause algae blooms, chemical runoff from factories

– Land: trash (the average American produces 1.8 kg of solid waste per day) and pesticides

• Poaching: removing species from their native environments

• Overuse: using natural resources faster than they can be replaced, ex. foresting, burning fossil fuels, overhunting, etc.

Conservation of Biodiversity

• The study and implementation of methods to protect biodiversity

• Natural resources: parts of the environment that are useful or necessary for living

organisms

• Examples include sunlight, water, air, and plant and animal resources

Ways of Protecting Biodiversity

• Protecting habitats by creating natural parks and preserves

• Sustainable use of certain areas– people can

harvest food or obtain materials but this activity is managed

• Reintroducing species– releasing organisms into an area where the species once lived

• Mr. Anderson’s Biodiversity podcast: http

://www.youtube.com/watch?v=0-PE3ve3w2w&sa fe=active

• Mr. Anderson’s Ecosystems podcast: http://

www.youtube.com/watch?v=Ot_KmOTYfRA&safe=active

• Mr. Anderson’s Cycles podcast (start at 4:30): http://

www.youtube.com/watch?v=09_sWPxQymA

• Mr. Anderson’s Succession podcast:

• http://www.youtube.com/watch?v=V49IovRSJDs http://

www.bozemanscience.com/science-videos/2012/5/6/ecological-suc cession.html

• Mr. Anderson’s Biodiversity podcast: http://

www.youtube.com/watch?v=0-PE3ve3w2w&safe=active

• Mr. Anderson’s Populations podcast: http://

www.youtube.com/watch?v=KFViSog6ZJw&safe=active