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What is Ecology?

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What is Ecology??• The study of interactions between organisms and their environment.

• Tells how living organisms affect each other and the world they live in.

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Habitat & Niche• Habitat- where a plant or animal lives

• Niche-an organism’s way of life (what it does)

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The Nonliving Environment

• Abiotic factors- nonliving parts of an environment.

• Examples: air currents, temperature, moisture, light, and soil.

• Abiotic factors affect an organism’s life.

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The Living Environment• Biotic factors- all the organisms in an environment.

• All organisms depend on others directly or indirectly for food, shelter, reproduction, or protection.

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Abiotic or Biotic?

Biotic

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Abiotic or Biotic?

Abiotic

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Abiotic or Biotic?

Abiotic

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Abiotic or Biotic?

Biotic

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Levels of Organization

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What are the Simplest Levels?

• Atom• Molecule• Organelle• Cell• Tissue• Organ• System

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Levels of Organization• Interactions of an organism

are placed into levels by complexity.

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1st Level of Organization• Organism:

An individual is• made of cells, • uses energy,• reproduces,• responds, • grows and

develops

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2nd Level of Organization• Population:

group of organisms, of the same species, living in the same place at the same time that interbreed

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Populations• Population Size

–Number of individuals in a population• Affects population’s ability to survive

• Ex. Smaller populations may be endangered by random events like natural disasters.

• Population Density–Number of individuals living

in a given area.

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Population Growth• Populations grow when more

individuals are born than die in a given period.

• Exponential Growth Curve- Rate of population growth is steady, so population size increases

exponentially.

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Exponential Growth Curve

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Resources and Population Size• Carrying Capacity

–maximum population (as of deer) an area can support without causing deterioration

• Density-dependent factors–resources that may be depleted by over population

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Logistic Model • Model that account for declining

resources effect on populations–When population is BELOW

carrying capacity, growth is RAPID.

–When population nears carrying capacity population growth slows down

–When population reaches carrying capacity, equilibrium is reached

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Logistic Growth

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Growth Patterns• R-strategists

–Populations grow rapidly

–Population size drops rapidly in poor conditions

–Short life spans–Many offspring–Little/no parental

care

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Growth Patterns• K-strategists

–Population grows slowly

–Density near carrying capacity

–Long life span–Few offspring–Long term

parental care

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Hardy-Weinberg Principle

• Frequencies of alleles in a population don’t change unless evolutionary pressures act on the population– These pressures are:

• Mutation• Gene Flow• Genetic Drift• Natural Selection

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Mutation• Any change in DNA

–Does not change allele frequencies

–Not all mutations affect phenotype

–Some mutations change a protein & how it works

–Others don’t…–Mutation rates are slow but

may make evolution possible.

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Gene Flow• The movement of

alleles in or out of a population

• Caused by migration of individuals in or out of a population gene pool

• This adds or removes alleles

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Non-Random Mating• Individuals mate with others

nearby or of their own phenotype– Ex. Female peacocks prefer

male peacocks with best tail plumage • Alleles for very full tails

tend to increase in a population

• Inbreeding– Choosing to mate with

relatives– Increases the number of

homozygous individuals in a population

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Genetic Drift• Any change in gene frequency,

especially due to disaster– Happens more often in small

populations– Ex. A fire breaks. Survivors carry

the polydactyl (multiple fingers and toes) allele.

– Soon, almost the entire population is polydactyl.

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Natural Selection• A change in the frequency of an allele

due to its effects on survival and reproduction.

• Ex. Individuals that survive a malaria outbreak carry a gene for mutated hemoglobin- the sickle cell gene.

• The frequency of this allele will increase due to repopulation.

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3rd Level of OrganizationBiological Community:All the different populations living in the same place at the same time.

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SymbiosisInteractions between closely

associated, interdependant species. These are• PARASTISM• COMMENSALISM• MUTALISM

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ParasitismOne species

benefits but the other is harmed (+/-)

• Ex. Leech sucking your blood!!!

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CommensalismOne species

benefits; the other is unaffected (+/o)

• Ex. Epiphytes grow on trees. They don’t harm or help the trees they live on.

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MutualismBoth species

benefit• Ex. Insects and

birds eat nectar from flowers. Pollen gets attached to their feet. At the next flower, they leave some, helping the reproduction of the plant.

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4th Level of OrganizationEcosystem:

Populations of organisms that interact with each other and with the abiotic parts of that area. (terrestrial or aquatic)

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Biomes• A major biological community that occurs over a

large area of land.– Examples

• Tropical Rainforest• Savannas• Deserts• Taiga• Tundra• Temperate Grasslands• Temperate Deciduous Forest• Temperate Evergreen Forest• Freshwater Communities• Wetlands• Shallow Ocean Waters• Surface of the open Sea• Ocean Depths

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Cycles in Ecosystems• Elements are recycled through

the environment– Carbon– Water– Nitrogen

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Water Cycle

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Carbon Cycle

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Nitrogen Cycle

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5th Level of Organization• Biosphere:The portion of Earth that supports life.

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The Biosphere

• Life is in the air, land, fresh water and salt water.

• The BIOSPHERE is the part of Earth that supports living things.

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What level of organization?

Organism

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What level of Organization?

Community

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What level of Organization?

Population