AP Biology Review Part 4 Animal Repro – Menstrual Cycle Ecology - Succession Ecology – Biochemical Cycles Genetics - Gene Regulation

AP Biology Review Part 4

Animal Repro – Menstrual CycleEcology - Succession

Ecology – Biochemical CyclesGenetics - Gene Regulation


• Animal Repro and Development– Menstrual Cycle


• Animal Repro and Development– Menstrual Cycle


• Ecology – Succession

• = the change in the composition of a species over time.

• Traditional view:– One community of species is replaced by another predictable

community of a different species.– Over time species diversity (number of species in a community) and

total biomass increase.– Eventually a constant species composition is arrived at = climax

community.– Climax community will persist relatively unchanged until it is destroyed

by some catastrophe (such as fire)

• Things are not always as predictable as once thought.


• Ecological succession– Primary succession

• Occurs in areas where there is no soil formation and there has never been previous life forms, such as volcanic islands or land where glacial retreat has occurred.

– Secondary succession• Occurs where there has been previous life, but it was completely or

partially destroyed by some kind of damaging event.– Fire damage– Floods– Abandoned agricultural fields, deserted lots


• Ecology – Biogeochemical Cycles– Flow of essential elements from the environment to living things

and back to the environment again.• Water (hydrologic) cycle

• Carbon cycle

• Nitrogen cycle

• Phosphorus cycle


• Biogeochemical cyclesWater Cycle Carbon Cycle Nitrogen Cycle Phosphorus Cycle

Storage location (reservoir)

Oceans,air (water vapor), groundwater, glaciers

Atmosphere, fossil fuels, peat, durable organic matter (such as cellulose)

Atmosphere and soil Rocks

How element incorporates into plants and animals (assimilation))

Plants absorb water from soil

Animals drink water or eat other organisms (which are mostly water)

Plants use CO2 for photosynthesis

Animals consume other animals or plants.

Plants absorb

Animals eat plants or animals

Plants absorb from soil

Animals eat plants and animals

How element returns to the environment (release)

Plants transpire.

Animals and plants decompose

Plants and animals release CO2 through respiration and decomposition.

CO2 is released when organic material is burned

Denitrifying bacteria

Detrivorous bacteria

Animals excrete

Plant and animal decomposition

Animals excrete


• Water Cycle


• Carbon Cycle


• Nitrogen Cycle


• Phosphorus Cycle


• Regulation of gene expression in bacteria– Operons – sequences of DNA, composed of:

• Promotor

• Operator

• Structural gene

• Regulatory gene that produces a repressor protein– (not actually part of the operon)

– Example; lac operon and try operon in E. coli


• Components of an operon– Promotor

– Operator

– Structural Genes

Short sequence of DNA where RNA polymerase first attaches to transcribe gene.

Short portion of DNA where repressor binds. When the repressor is on the operator, RNA polymerase can’t bind to the promoter.

One to several genes coding for enzymes of a metabolic pathway.



• The lac Operon– When glucose is not available to E.coli, it can use lactose instead (if

available).

– Normally doesn’t make the 3 enzymes needed for lactose metabolism.

– If those enzymes are needed, E. coli can immediately start to synthesize them.

– Click for animation of “normal” situation – cell doesn’t need enzymes to digest lactose.

Enzyme 2: Permease

Facilitates lactose entry into cell

Enzyme 3: Transacetylase

Accessory function in lactose metabolism

How do we do it!?

Enzyme 1: B–galactosidase

Lactose glucose and galactose


• The lac Operon– The 3 genes are next to each other on a chromosome.– They are all controlled by the same operator and same promoter.– Normally, regulator gene makes an active repressor that binds to the operator

(which prevents RNA polymerase from binding to the promoter).– When lactose is present –it binds to the repressor, changing the repressor’s

shape.– Repressor can no longer bind to operator, so genes are transcribed enzymes

are made.– This is an inducible operon because lactose induces enzyme synthesis.

Inducible operons are usually turned off-they are induced to turn on, and are usually associated with metabolic systems that break things down.Repressible operons are usually turned on-they are repressed to turn off, and are usually associated with systems that synthesize things.



• The Trp Operon– Operon in E. coli that is usually turned on.

– Codes for 5 different enzymes that are part of the anabolic pathways of tryptophan (amino acid) synthesis.

– Regulator gene codes for a repressor that normally can’t bind to operator.

– What happens if E. coli is grown on a media that already has tryptophan in it? (see next slide)

– Click for animation – normal situation – tryptophan needs to be made.


• The Trp Operon– If tryptophan is present in media

• Enzymes aren’t needed, so try operon turned off– Tryptophan (from media) binds to repressor changes shape of repressor so can now bind

with operator. RNA polymerase unable to bind to promoter.

– This is an example of a repressible operon and tryptophan is called the co repressor.

– Repressable operons usually associated with anabolic pathways.



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AP Biology Review Part 4 Animal Repro – Menstrual Cycle Ecology - Succession Ecology – Biochemical Cycles Genetics - Gene Regulation