Ecology II
II. Connections
a. Carrying Capacity & Biotic Potential
The biotic potential, which is the maximum rate of increase per individual for nay population that is growing under ideal conditions, will eventually lead to the carry capacity of a population. The carry capacity is the maximum number of individuals of a population that a given environment can sustain indefinitely. If the biotic potential reaches 100%, it will fulfill the entire carrying capacity.
b. Biological Magnification & Trophic Level
Biological magnification occurs in trophic levels. The concentration of a slowly degradable or non-degradable substance in body tissues increases as it passes along food chains. If a primary producer has a concentration of x1 pollution, that number will consistently increase as it is eaten by a primary consumer, increasing to x2. This increase remains constant as secondary and tertiary consumers eat their prey in the lower trophic level.
c. Detritivores & Autotrophs
Detritivores are organisms that obtain their energy by consuming dead plants and animals. Autotrophs are primary producers who convert the sunlights energy into chemical energy. The autotrophs are the first trophic level because they are the source of all chemical energy for other organisms to consume. Detritivores are the last trophic level because they consume all the energy that was consumed by the other trophic levels.
d. Mitochondria & Greenhouse Gases
Wavelengths in rays from the sun warm the surface of the Earth. The surface radiates heat, infrared wavelengths, to the atmosphere. Greenhouse gases and water vapor absorb some infrared energy and radiate a portion of it toward back toward Earth. Increased concentrations of greenhouse gases, for example, the increases concentration of carbon dioxide in the winter when photosynthesis rates decrease but aerobic respiration in the mitochondria still occurs, trap more heat near Earth's surface causing the temperature to rise.
III. Few Essentials
a. 45.4 Outline
I. Limits on the Growth of Populations
A. Density-Dependent Limiting Factors
1. environmental circumstances keep population from fulfilling biotic potential
2. limiting factors affect population growth
B. Carry Capacity and Logistic Growth
1. sustainable supply of resources will determine population growth
2. pattern of logistic growth can show the effects of carrying capacity
3. when overcrowding occurs: density-dependent controls
C. Density-Independent Limiting Factors
1. can cause more deaths or fewer births
2. regardless of population density
b. 3 Survivorship Curves
Type 1: reflect high survivorship until fairly later in life, then a large increase in deaths.
ie: large mammals, such as elephants, have one or a few large-bodied offspring at a time, then engage in an extended parental care
Type 2: reflect a fairly constant death rate at all ages
ie: organisms just as likely to be killed of die of disease at any age, such as lizards
Type 3: reflect a death rate that is highest early in life
ie: species that produce many small offspring and do little parenting, such as sea stars
c. Age Structure Diagrams
1. A population undergoing negative growth: The base of the diagram representing pre-reproductive years is much smaller than the top of the diagram representing post-reproductive years. The maximum population growth is at the early post-reproductive years, around age 45.
2. A population with nearly no growth: The base of the diagram stays almost the same width all the way up towards the start of the post-reproductive years. It starts to decline after that showing a consistent death rate in those ages.
3. A population growing rapidly: The base of the diagram is way more than twice the size of the rest of the diagram. It consistently decreases its width towards the top, resembling almost nothing at the highest ages.
4. A population growing slowly: It shows a steady decrease in width going from the base of the diagram to the top. There is a very small difference between the number of pre-reproductive year people than post-reproductive year people.
d. The Nitrogen Cycle
Nitrogen in abundant in the atmosphere in its gaseous form of N2. This form of nitrogen is useless to plants and animals, so it needs to be converted to a solid form. Nitrogen fixing bacteria convert the N2 into NH4. Nitrifying bacteria convert the NH4 to NO2, nitrites, and NO3, nitrates. Plants can then absorb the NO3 and pass it to animals who consume the plants. After the animals and plants die, detritivores break down their matter and release the nitrogen back to the soil through ammonification.
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