Ch. 45 & 47 & 48

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.

Ch. 46 & 49

Ecology 1


2. Connections

a. Co-evolution & Commensalism

Co-evolution refers to species that evolve jointly when their interaction produces selection pressure on each other.  A gene mutation may occur causing a prey to increase defense mechanisms, or a predator to catch its prey more efficient.  Commensalism is the interaction between two species, where one benefits and one is not affected.  If co-evolution occurs, it could disrupt the commensalism between the species, causing the neutral one to become harmed or to benefit.

b. Mimicry & Aposematic Coloration

In mimicry, a mimic organism resembles a model organism very closely in form and behavior.  An organism develops aposematic coloration after eating its prey and associating its appearance to the toxins and foul taste it receives.  An organism can develop aposematic coloration on either a mimic or a model involved in mimicry and become now confused on what it is supposed to eat.  Its prey may be the model organism, but if the mimic is eaten, the predator will not eat its real prey because it has developed an aposematic coloration on it.

c. Altruism & Allele

Altruism is a self-sacrificing behavior, where an individual helps a population by reducing its own chance of producing offspring.  An allele is a molecular form of a gene normally developing from a mutation.  An organism who experiences altruism may gain an allele that reduces its reproduction chances.


d. Species & Population & Niche


A niche is the sum of its activities and interactions a species acquires to use the resources it must have to survive and reproduce.  The niche of a species and how well the species can adapt its niche to work with its environment will determine how will it will survive among its population.


3. Few Essentials


a. Examples of the following concepts and interactions


1. Commensalism: The sparrow, a small bird, builds its nest under the nest of the osprey.  The osprey is a larger bird that protects the sparrow's nest without knowing its there.


2. Mutualism: Lichen is a half plant half fungus.  The plant provides food for the fungus, while the fungus provides protection from radiation and water absorption.


3. Parasitism: Tapeworms enter the human body and live in the intestines.  It feeds off of the nutrients the human eats, causing the human to keep eating but not gain any nutritional support.  The human dies from malnutrition.


4. Resource Partitioning: The bristly foxtail and the smartweed plant live in the same field, but need to gain the same requirements, such as sunlight, water, and minerals.  The bristly foxtail has a shallow root system, allowing it to grow where moisture shifts daily.  The smartweed has a taproot system, allowing it to grow where soil is perpetually moist.


5. Predator-prey Co-evolution: The snowshoe hare, due to its predation, constantly looks over its shoulder with alert and in fear.


6. Camouflage: A caterpillar can look like birds droppings if it has special color patterns.


7. Mimicry: Beetles and flies can mimic the appearance of the model yellowjacket to avoid being eaten.


8. Aposematic Coloration: A bird can develop aposematic coloration after eating a certain orange-and-black butterfly.  The bird will associate the butterfly's color to the toxins and foul taste it had.


9. Pioneer Species: Douglas firs started to grow in the Cascade area at the bottom of the Mount St. Helen volcano a decade after the volcano erupted.


10. Keystone Species: Periwinkles, algae-eating snails, help maintain the number of algal species in tidepools, but reduce it on exposed rock surfaces.


11. Instinctive Behavior: A human baby imitates the facial expressions of adults out of experience before learning them.


12. Imprinting: Baby geese follow their mom around during their short, sensitive period after hatching.


13. Altruism: Zebras are eaten by lions to help the lion population grow.


14. Chemical Communication: The honeybee sends chemical alarms to call action against potential threats.


15. Tactile Communication: When a honeybee finds a source of pollen or nectar, it performs a dance, keeping close contact to the other bees to signal to them the information about about the food source.


16. Courtship ritual/display: King penguins tilt their necks towards each other as a sign of affection.