Bacterial transformation can be a natural or a manipulated (artificial) process that provides a mechanism for the recombination of genetic information in some bacteria. Small pieces of extracellular DNA are taken up by living bacteria, ultimately leading to a stable genetic change in the recipient cell. • A Plasmid is a small circular piece of DNA that is contained in the bacteria.

You can take the DNA from two different organisms and recombine them together in a new DNA molecule, and then transform another organism giving it the desired trait.

How to do it:

• Use restriction enzymes (which “restrict” the specific segment of DNA to be cut, and lyse it out)

• These restriction enzymes recognize certain DNA sequences by their “recognition sequences”.

• The “sticky ends” of the cleved DNA fragment join up readily with new DNA

Hundreds of restriction enzymes have been isolated:

• EcoRI; BamHI; HindIII

The human gene for insulin production has been successfully inserted into E. coli, where it produces insulin which is then isolated and used to treat the disease.

Gel electrophoresis is a method used to separate restriction fragments of different lengths, as they diffuse through the gel.

A virus is a parasitic particle that can live only inside another cell. The cell that it “infects” (as they are pathogens) is tricked into producing the proteins that the virus needs to make more viruses. It does this through hijacking the pathway to protein synthesis.The basic structure of the virus is a DNA or an RNA enclosed by a protein coat called a capsid.Viruses are cell-specific, and can only infect certain kinds of cells.

This is because the virus gains entrance into a cell by binding to specific receptors on the cell surface. The AIDs virus (HIV) can only bind to the surface of Helper “T” cells.

• Some viruses initiate an infection into cells, and then may remain dormant inside host cells for long periods, causing no obvious change in their host cells (a stage known as the lysogenic phase).

Lysogenic (DORMANT)

• When a dormant virus is stimulated, it enters the lytic phase: new viruses are formed, and burst out of the host cell, killing the cell and going on to infect other cells.

Lytic (ACTIVE)

In this cycle, viruses replicate without destroying the host cell. The phage (virus) becomes incorporated into a specific site in the host’s DNA. It remains dormant within the host genome and is called a prophage. As the host cell divides, the phage is replicated along with it, and a single infected cell gives rise to a population of infected cells. At some point, the environment triggers the prophage to switch to the lytic phase.

The phage enters the host cell, takes control of the cell machinery and forces the cell to replicate viral particles. The cell replicates more viral particles to be manufactured, which are assembled into viruses. This will cause the host cell to lyse (rupture) killing the host, and the viruses are spread then to new host cells.

A virus that contains RNA instead of DNA is a retrovirus. These viruses replicate in an unusual way.

• Virus injects genome into host cell

• Their RNA serves as a template to build a cDNA (complementary DNA)

Examples of retroviruses are:

HIV, and polio

• This reverse transcription occurs with the help of the enzyme reverse transcriptase.

•Population

• Community

• Ecosystem

• Biosphere

• Habitat

• Niche

A group of individuals all of the same species in a defined geographical region.

A group of species in a defined geographic region.Relationships between organisms and environment.All regions of the Earth

that contain living things.

Levels of Ecological Organization:

The place where an organism lives.

The role an organism plays in its environment, such as producer; consumer; decomposer; diurnal; nocturnal; ground dweller; mates for life; egg layer…etc.

The size of a population is represented symbolically with the letter N, which is the total number of individuals.

Populations can be dense…that is many individuals in a given area, or diffuse, only a few in a given area.

Individuals may be dispersed in a population uniformly, randomly, or in clumps.

Through an age structure diagram, the age structure of a population can be studied, showing the abundance of individuals of each age.

By analyzing the graphic structure, you can determine whether the population is growing rapidly, slowly, or not at all.

The biotic potential is the maximum growth rate of a population under ideal conditions, with unlimited resources and without any growth restrictions.

Some bacteria have the potential to produce over a trillion offspring within ten hours! The following factors contribute to the biotic potential of a population:

• Age at reproductive maturity

• Clutch size

• Frequency of reproduction

• Reproductive lifetime

• Survivorship of offspring to reproductive maturity

The carrying capacity is the maximum number of individuals of a population that can be sustained by a particular habitat. It is often evident on a graph of population growth.

“S” or “J” type shapes on a population graph are typical of exponential growth patterns.

• Log phase

• Carrying Capacity

Once the population reaches carrying capacity, if you add more individuals, you are inviting catastrophe! The population plunges.

If the environment has not been irreparably damaged, the population may rebound

A limiting factor is any element that prevents a population from attaining its biotic potential. Limiting factors are categorized into:

Density-dependent

• Density-independent

Those agents whose limiting effect becomes more intense as the population density increases. Examples include parasitic infections, disease, competition for resources, and the toxic effect of waste products. Predation is also density-dependent!

Factors which occur independently of the density of the population, such as natural disasters, and extremes of climate.

Species have different reproductive patterns that can help enhance their survival.

• High reproductive rate (r) : r-selected species

These species usually have many small offspring, and give them little or no parental care.

They overcome potential offspring loss by producing so many.

r-selected species do relatively well in unstable or unpredictable environments.

Other r-selected Traits Include:

• early maturity onset• short generation time

Organisms whose life history is subject to r-selection are often referred to as r-strategists or r-selected.

• bacteria and diatoms, • insects • weeds• semelparous cephalopods • mammals• reptiles

What exception to the rule do mammals exhibit, that none of the other groups do?

They nurture and care for their young for an extended period of time.

In stable or predictable environments, K-selection predominates as the reproductive strategy.

Unlike r-selected populations, where population size can change dramatically overnight, K-selection populations are typically close to the maximum that the environment can bear (carrying capacity) at most times.

The ability to compete successfully for limited resources is crucial for that reason.

K-Selected Traits Include:

• Large body size

• Longer life expectancy

• Fewer offspring

• Extensive parental care

Although some organisms are identified as primarily r- or K-strategists, the majority of organisms do not follow this pattern.

• Trees have traits such as longevity and strong competitiveness that characterize them as K-strategists.

• In reproduction, however, trees typically produce thousands of offspring and disperse them widely, traits characteristic of r-strategists.

• Sea turtles display both r- and K-traits: although large organisms with long lifespans (should they reach adulthood), they produce large numbers of un-nurtured offspring.

If you suddenly stopped cutting the grass in your yard, what would it look like in a year?

In 10 years?

You don’t have to be an ecologist to know that your grass would grow longer, and that weeds would take over your yard if you let them.

Your yard would resemble a meadow, with small bushes and shrubs, but still mostly grasses

What about in 50 years?

The bushes and trees change the environment. Less light reaches the ground as they grow taller, and grasses eventually die out.Succession occurs in stages, and can often take decades or even centuries to occur. There are two types of succession:Primary and Secondary

Primary succession occurs on barren land, where there are and have been no living organisms in the past.

This occurs when the land is new, and has never been colonized by organisms before.

These organisms of primary succession are known as “pioneer species”.

Primary succession occurs in previously uninhabited areas with no soil.

When a natural disaster such as a forest fire destroys a community of living organisms, and nature takes over to replace these organisms, then secondary succession begins. Severe disruption of an existing community is the key factor in this type of succession.

Mirror Lake, Yosemite

Mirror Meadow, Yosemite

Secondary succession occurs where there is developed soil on the ground. It is much faster than primary succession.After time passes, succession slows down, and the community becomes fairly stable. A stable mature community that undergoes little or no change in species is known as a climax community.

The nutrient cycles you should be thoroughly familiar with are:• Carbon, • Hydrologic, and • Nitrogen. The hydrologic cycle helps the phosphorus cycle out, by eroding the rocks, and releasing the phosphorus into the soil, and water.

It is taken up by plants and animals, and then when they die, it is added back to the soil, where it has the potential to be made into rocks again!

You may also see the phosphorus cycle show up on the AP test. This is the simplest cycle. Most of the phosphorus found in the phosphorus cycle originates in the rocks beneath your feet. (if a cycle has an origin).

The carbon and hydrologic cycles are also quite easy. Remember the following:

Hydrologic cycle Processes:• Evaporation: liquid to a gas• Condensation: gas to a liquid (clouds)• Precipitation: liquid or solid to the ground• Runoff: over the ground• Infiltration: Into the ground• Transpiration: Plants participating in the cycle as water vapor moves through the stomata of a plant.

Carbon cycle Processes:• Photosynthesis: Plants manufacture glucose, and take CO2 in, Oxygen out• Respiration: Both cellular, and breathing…it is the exchange of gases O2 for CO2. (opposite of photosynthesis) Process breaks down glucose to produce ATP• Decomposition releases CO2 back to atmosphere• Largest Carbon sink: Ocean (dissolved CO2) and shelled organisms (CaCO3)

Carbon is also found in our fossil fuels, and when we burn them (combustion), we add the original carbon from the organisms that fossilized, back into the atmosphere.

Of all the nutrient cycles, the Nitrogen Cycle is the most difficult to understand, because of all the different stages. Stages of the Nitrogen Cycle to Remember:

Nitrogen Fixation: Soil bacteria convert N2 (atmospheric nitrogen) into ammonia (NH3)• Nitrification: Nitrifying bacteria convert the ammonia into nitrate.• Assimilation: Nitrate is assimilated and absorbed by plants (which are consumed by animals to pass the nitrogen on in the food web) This nitrogen in plants is used to help make amino acids, the building blocks of proteins.• Ammonification: After death, ammonifying bacteria break nitrogen compounds in the body down, and return them back to the soil in the form of ammonia.• Denitrification: Denitrifying bacteria can take nitrates and convert them into atmospheric nitrogen again, completing the cycle.

Polar Tundra; Taiga (Boreal Forest); Temperate Deciduous Forest; Grasslands; Desert; Rainforest; Marine and

Freshwater

• Camouflage

• Hibernation

• Thick coats and extra fat• Migration

• Cold…low growers

• Wet…large leaves with drip tips

• Hot and dry…small surface area, extensive roots close to surface

• Cold winters, hot summers

• Dry and warm