Lecture Notes-06 Biology 1004

North Arkansas College

Topic: Ecology

Click below for discussion and further links.

http://pbil.univ-lyon1.fr/Ecology/Ecology-WWW.html

http://conbio.net/VL/search/

Energy is required to do work; to carry on vital processes. Input of energy is required to maintain an ordered system and for key metabolic events. Form of energy as it flows through system; heat ATP (adenosine triphosphate); 1 ATP = 6,000-12,000 calories of energy. There are groups of organisms involved in cycling of energy in living systems.

1. Population; A number of the same species inhabitating same area.
2. Habitat; Location where organisms are found
3. Community; Several types of species living together in one area.
4. Ecosystem; Communities of organisms interacting with their physical environment.
5. Biosphere; All of ecosystems on Earth.

Communities and ecosystems interact with each other to cycle nutrients, etc. In doing so, they form:

1. Niche; Location, interaction of individuals, and activities of organisms in a habitat that provides all resources for survival.
2. Competition; Interaction in which one or more species compete for a niche (habitat). Competition is necessary. In the Rockies, the Broad Tail Hummingbird is the dominant species. In mid- to late August, the Rubar Hummingbird from the Northwest arrives (a more aggressive species), and it drives the Broad Tail out of the area.

1. Nature of Populations - useful to know the size and the distribution of population(s).
2. Measurement of Populations- population numbers become important in a number of ways to form a foundation (set of data) to study changes and dynamics of population.

1. Directly by tagging or marking individual species in a population.
2. Indirectly by counting number of tracks, droppings. 

1. J Type Growth Curve - growth is sequential rather than arithmetic. In J shaped curves the initial population increase begins fairly slow but gradually the population begins to increase exponentially.

2. S Shaped Growth Curve - The first part is similar to the J shaped curve, however eventually because of environmental resistance the growth will gradually begin to slow down then stabilize.

Point at which growth stabilizes is K.

K is the point of which population stabilizes. If it were to continue it would begin to decline.

What type of environmental resistance can cause this?

3. Environmental Resistance may be due to:

1. Food Supply
2. Drought
3. Temperature Changes
4. Toxic Substances

4. Calculation of Growth Rates-the difference between the birth and death rate.

1. Birth Rate-the number of births proportional to the total population in a geographical region. Ex: 2 births per 100= 2%

2. Death Rate- the number of deaths in proportional to the total population in a geographical region.

3. Growth Rate-The difference between the birth and death rate.

Denoted by r and even a small difference in r, can influence dramatically the population size and dynamics.

If r is less than 0, the growth rate is declining.

If r is exactly 0, then it is staying the same. (0 population growth).

If r is more than 0, the growth rate is increasing.

Intrinsic Growth Rate - What is the potential for growth if external forces were not a factor?

Each species has a Characteristic Rate of Growth.

Example: Water Flea. Bacteria, etc. have a very high growth rate or r value.

Example: Whales. Elephants. Humans, etc. all have a lower growth rate (More influenced by environmental factors).

In reality, environmental resistance impacts growth rates either as K or r factors type of growth.

K growth patterns are more dramatically influenced by the density of a given species in a geographical area. This is called caring capacity, which is the maximum number of individuals that can be cared by the ecosystem without environmental resistance (K) influencing it.

In reality K, is not fixed in population. Regardless of type of population they tend to fluctuate or hover slightly above or below K.  

K is very important in establishing/maintaining the population itself and predicting population change.

The closer a population comes to K it will begin to be impacted by environmental resistance and the growth rate will be level out.

1. K- Selected Species- Large animals

1. Reproduction rate is slower.
2. Population size is limited by caring capacity.
3. Environmental pressures are density dependent.

2. r- Selected Species- Flies, Mosquitoes, etc.

1. Opportunistic species live in highly variable environments.
2. High growth rates (exponential) produce large numbers of populations is to take advantage of favorable environments when they exist.

3. In reality r and K dependent species are distributed along a continuous line. These dependencies for K and r are collectively termed reproductive strategies.

1. In general, smaller species are more dependent on the r end of the spectrum.
2. In general, K species are larger species because they depend on carrying capacity or population density (Low reproduction or low growth).
3. Many species actually fall in the middle and can adapt to either end.  They exhibit variations.

Think About World Population

Basically two curves exist.

1. Survivorship occurs- estimate death rates (for insurance companies rates)
2. Population pyramids- they depict distribution of age in a population with emphasis on that portion which precedes or is capable of reproduction.

Ex. Kenya

Large part of population is at or preceding reproductive years, we would expect high growth rates.

In contrast slower growing communities or countries such as the US. have populations that are either at or beyond their reproductive years. We would expect this population to become stable or may even begin to decrease.

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