Ecology

1
Ecology

• Its about relationships and maintaining balance

2
Symbiotic Relationships

• Symbiosis literally means living together
• Creatures involved in symbiotic relationships are
  linked together closely
• Some symbiotic relationships help the members of
  the relationship
• In some symbiotic relationships, members are
  harmed

3
(No Transcript)
4
Neutral Interactions are not symbiotic - the
creatures do not affect each other
5
Commensalism involves one creature benefiting and
the other not being affected
6
Mutualistic Relationships benefit both creatures
involved
7
Interspecific competition is avoided because it
harms both species involved
http//www.wildlife-pictures-online.com/cheetahkil
l.html
8
Predation helps one member and kills the other
9
Parasitism helps one and harms the other
10
Predator - Prey relationships deserve further
attention
11

• It is difficult to find good examples of natural
  interactions that have been monitored over long
  periods of time. . .
• Data collected from a fur company encompassed
  pelts from lynx and their prey, snowshoe hares,
  over an eighty year period of time
• This data revealed several factors concerning the
  predator-prey relationship
• There must always be more prey than predator
• Both populations fluctuate over time
• The prey drives the predator the predator
  population responds to the prey population
• Parasite-host relationships follow a similar
  pattern

12
Prey have developed several adaptations to avoid
predation

• Camouflage
• Mimicry
• Warning coloration
• Speed, claws, fangs, bad smell, quills, shells,
  armor, puffing up, behaviors, and many others

13
Can you find these animals?
14
Ecological Niches

• There is a niche for every organism and it
  includes the organisms adaptations, its use of
  resources, and its lifestyle
• The potential niche for an organism is broader
  than the actual filling of the niche (realized
  niche)
• An organism may need to shift niches (be
  adaptable to more than one) due to competition

15
Niches are defined by limiting factors and the
range of tolerance an organism can withstand
16
Law of the Minimum

• Numerous factors, both biotic and abiotic need to
  be in optimum amounts for the best growth
• Precipitation, temperature, competition for
  resources, predation, soil mineral content, etc.
• The growth of each organism is limited by
  whatever factor essential to it, is in shortest
  supply or is present in harmful excess.

17
Ecology

• Population Genetics and Community Stability

18
Population Biology

• A population is a group of the same species
  capable of interbreeding and living in the same
  geographic area

• Population Density is the number of individuals
  of a species per unit of habitat area. The
  density can vary within a habitat. Variations
  are caused by external factors in a habitat.

19
Distribution patterns

• Random distribution
• Uniform distribution
• Clumped distribution

20
Distribution patterns of organisms in their
environment

• Random distribution seems likely, but it is not.
  Environmental factors that cause distribution do
  not occur randomly
• Uniform distribution is a bit more common due to
  territorial behavior
• Clumped distribution is the most common. Family
  groups - social animals benefit from mutual aid
  and family groups. In plants - seeds tend to
  disperse close to source and asexual clones are
  close to the source.

21
Biotic Potential

• Biotic potential is the maximum rate at which
  organisms could reproduce under ideal conditions
• Factors would include maximum litter size,
  maximum recruitment, full reproductive span

22
Factors influencing biotic potential

• Type of reproduction - bacteria reproduce
  asexually and have very high biotic potential
• Niche of the organisms - mice vs. wolves
• Number of offspring produced, frequency of
  reproduction, length of reproductive life
• Mortality is the inverse of biotic potential and
  is affected by environmental resistance

23
Survivorship curves
Very high mortality for offspring - tree seeds,
oyster offspring - those that survive live long
This is very common - dangers in the environment
keep death rate constant
Humans have Type I survivorship - high in youth
24
S curve growth occurs when biotic potential is
balanced by environmental resistance and carrying
capacity is reached
J curve growth phase exponential growth
Lag phase -low initial growth
25
K carrying capacity. If sustained, the maximum
number of individuals an area can support without
causing damage to the area If K is not sustained
and the carrying capacity has been exceeded, then
two possibilities A population crash - an abrupt
decline from high population density to very low
density. This can result in extinction (can
easily be seen with cultures in confined area -
all needed resources are consumed and do not
regenerate fast enough or are nonrenewable A
partial population crash - an abrupt decline from
high population density to below previous
carrying capacity. These may stabilize, but at a
carrying capacity lower than the previous level.
26
(No Transcript)
27

• Environmental Resistance - factors that limit
  population growth
• Limiting factors - Essential elements that hold
  population size in check (too much or too little
  moisture for big bluestem grass)
• Density- independent limiting factors - Random
  events that limit population size ( storms,
  hurricanes, blizzard, collision with an asteroid)
• Density-dependent limiting factors (become more
  intense with higher population densities)
• Resource depletion - water, minerals, etc.
• Competition for resources occurs in and between
  all populations (If one group fails to get the
  minimum of needed resources - this leads to
  mortality, even extinction)
• Competition for space (includes food and cover
  for animals) Territoriality divides up space
  between animals. Overcrowding for mobile animals
  causes stress and aberrant behavior (mice eat
  their young, etc.)

28
Community Complexity

• When all populations are in dynamic balance,
  another factor important to ecosystem health is
  the amount of diversity contained within the
  community
• Ecosystems health can actually be measured with
  diversity indices

29
Factors affecting diversity

• Diversity is related to abundance of potential
  ecological niches. More complex ecosystems tend
  to become even more complex. (Simple ones do not)
• Diversity is inversely related to isolation.
  Islands tend to show less diversity than similar
  continental ecosystems.
• Diversity is inversely related to stress and
  extreme environmental conditions. Stressed
  communities contain only those species capable of
  withstanding the stresses.
• Diversity bears a definite although complex
  relationship to ecological succession.
• Edge effect - diversity is often higher at
  margins of distinct habitats rather than in the
  center

30
Factors affecting Diversity

• Diversity is reduced when any one species gains
  exceptional dominance - outcompeting and crowding
  out other species.
• Diversity is greatly affected by biotic history.
  Longer times since establishment tends to have
  greater diversity. (Amazon rainforest has
  greater diversity than the rainforest of Belize.)
• It is believed that rainforests (the most complex
  of all ecosystems) owes its diversity to its
  history rather than other factors. Community
  complexity is due to long term community
  stability.

31
Ecological Succession is the process of community
change

• It is a natural and good process
• Primary succession - starts in a barren area -
  bare rock, glaciated area, after volcanic
  eruption
• Secondary succession - takes place in a habitat
  that has already been modified by a preexisting
  community - abandoned fields, forest fires,
  extensive logging

32
Primary Succession
33
Secondary Succession
34
Aquatic Succession
The silting-in and conversion of a pond to a
marsh or swamp and finally to a terrestrial
ecosystem is a natural progression.
35
Why does succession take place?

• Succession is the result of physical and chemical
  changes originating outside the community
• The goal of succession is to reach a climax
  community
• Climax communities are very stable. They will
  change, but the changes happen very slowly