Biology 1407 Exam 4 Notes - Ecology Ch.35 - 36
Ecology - scientific study of how individuals interact with their environment
34.1
- organisms have adapted to - evolved in - a particular set of conditions; the “context” of
adaptation
34.3-.4
- organizational levels of biology: 1.2, 34.1
biosphere
ecosystem
What are emergent
community
properties and why
population
are they important to
organism (individual)
the study of biology?
organ system
List several emergent
organ
properties of the levels
tissue
of organization studied
cell
in ecology
organelles
molecule
atom
Brief history of ecology
- practical effort for all of human history
- Greeks of 2500 years ago to early 1900’s descriptive ecology
- middle 1900’s to present experimental ecology
Populations
36.1
- all of the individuals of a single species (can interbreed to produce fertile
offspring) in one area
- “local species”
- individuals that have a high probability of breeding - a breeding unit
Ecologists have identified several properties of population:
1. Density - number of individuals in an area or volume of habitat
36.2
- crude density is number of individuals per total area
- ex. 1500 large-mouth bass / total surface area of Lake Leon
= 1500 bass / 300 hectares or 5 bass / ha
- easier to measure but less useful
- ecological density is number of individuals per usable habitat
- ex. 1500 bass / area of lake that bass use in Lake Leon
= 1500 bass / 100 hectares or 15 bass / ha
- more difficult to measure but more useful
2. dispersion
36.2
- distribution of individuals within population; how individuals are located in relation to
other individuals
- random distribution
-no positive or negative interactions between individuals; located by chance
ex. plants grow where their seeds have landed
- clumped distribution
- individuals occur in groups
- results from either positive social interactions
ex. schooling fish
- or individuals using a clumped resource
ex. turtles live in shallow area of lake with some vegetation and basking
sites
- uniform distribution
- even space between individuals
- results from either negative social interactions
ex. plants with root poisons or territorial lizards
- or individuals using uniformly distributed resource
ex. lizards seeking shelter in uniformly distributed creosote bushes
Distribution may change through time (deer grazing in random pattern during the day but
clumped at night; toads in breeding colonies during the spring but widely and randomly
distributed the rest of the year)
Important to consider biologically real area and changing pattern through time.
3. survivorship in population
36.3
- chance of an individual surviving each age period to old age;
when during its life an average individual will die
- based on life tables, expressed as survivorship curve
*How is survivorship related to the number of offspring produced and the effort devoted
to each offspring?
4. Age and sex structure of the population
36.9-.10
- percent of population in each age class, for females and males
- typically individuals (age classes) are pre-reproductive (not mature enough to
reproduce), primary reproducers, then post-reproductive (too old to
reproduce or contribute very few offspring)
- useful in predicting future population size.
*How does age structure relate to a population’s ability to increase?
*How do game managers use this information to determine hunting regulations?
*What is population momentum? How does it affect future population size?
5. Population growth
- change in number of individuals through time, G = rN
- numbers change due to:
- birth rate (natality)
- death rate (mortality)
- immigration (individuals moving in)
- emigration (individuals moving out)
36.4
- r = average increase, or number of offspring produced minus deaths, per individual
- rmaximum is growth under ideal conditions
- intrinsic rate of increase or biotic potential; what is biologically possible
- leads to exponential growth
- r actual = actual growth rate for the population at certain time
- ideal conditions do not last long, growth decreases due to limiting factors
- leads to logistic growth, with population leveling off at the present
carrying capacity ( K ), G = rN (K-N/K)
- population numbers typically fluctuate around K
- anything that changes rates of natality, mortality, immigration or emigration is a
regulating factor
35.5, 35.8
Some regulating factors are density dependent
36.5
- their affect is related to population size
- as population size increases death rate and emigration rate go up and/or birth
rate and immigration rate go down
- population size begins to decrease
- as population size decreases birth rate and immigration rate go up and/or death
rate and emigration rate go down
- population size begins to increase
ex. : - competition among individuals for resources such as food, nesting sites,
territory, etc.
- increased transmission of infectious disease and parasites
- predation increases or becomes more effective
- accumulation of toxins or other substances
- physiological or psychological stress, abnormal behavior
- these factors tend to stabilize population around carrying capacity; leads to
logistic growth
Some factors are density independent
- their affect is not related to population size
- ex. abiotic factors such as fires, floods, freezes, habitat disruption, etc.
- these factors tend to cause unstable population size with fluctuation in numbers.
Sustainable resource management important
- gives most resource over long time period
- maximum growth rate is important in resource management
- maximum sustainable yield when N = 1/2K
*What does the term sustainable mean?
*How is it an important concept in resource management?
*Describe the “tragedy of the commons” effect.
*What is carrying capacity for a population? Is it always the same for a population?
Human population growth during the last 10,000 years
36.9-.11
*What is the carrying capacity of Earth for humans?
*What is the “doubling time” for the human population and how has it changed?
*What kind of regulating factors will limit human population growth?
- shortage of resources such as water, area and quality of agricultural land, food
- accumulating toxins
- loss of biodiversity, overexploitation
*What is an acceptable standard of living?
*How equitable should this be for all countries?
Fig 36.11
*What is an ecological footprint and how does it relate to equitable standard of living?
(20 % of people in developed countries use 86 % of resources)
6. Life history
36.7
- events from birth through reproduction to death
- how an average individual lives and reproduces (divides energy between growth
and reproduction)
- natural selection favors the combination of life history traits that produce the
most offspring that survive and reproduce (viable fertile offspring)
= reproductive success
- evolutionary adaptive set of traits, not a conscious plan
- life history traits are trade-offs between reproduction and survival
- different populations may develop different life histories - what works best in
their particular environment
Some of the most important life history traits are:
- age at first reproduction (early offspring vs. better established parents)
- number of reproductions during a life time (all at once “big bang” vs. repeated
“not-all-eggs-in-one-basket”)
- effort into each reproduction (percent of female’s energy vs. chances of
future survival)
- effort into each offspring (many small offspring vs. few large offspring)
Life history “strategies” have been identified:
r - selection or opportunistic life history
- typical in unstable and unpredictable environments; density independent
regulating factors dominate
- emphasis on quantity of offspring; rapid production of many offspring is
most important
- develop the following set of traits:
- early age of first reproduction
- single breeding season
- large effort into each reproduction
- large clutch size
- small offspring
- no parental care
K - selection or equilibrium life history
- typical in stable and predictable environments; density dependent
regulating factors dominate
- emphasis on quality of offspring; the competitive ability of offspring is
most important
- develop the following traits:
- older age at first reproduction
- multiple breeding seasons
- small effort into each reproduction
- small clutch size
- large offspring
- have parental care
Most populations live in environments between these extremes, and therefore have a life
history between these extremes.
7. Behavior
Ch 35
- what an organism does and how it does it
35.1
- evolutionary adaptations to the environment; behavioral ecology
Innate behaviors – strongly genetically controlled
- most individuals in population do the same
- fixed action patterns triggered by specific stimulus
Learned behaviors – modified by experience
35.2
35.4Table
Social behaviors
35.12 - 20
- any interaction between individuals in the population (courtship and
mating, aggression, hunting or defensive cooperation)
- some form of communication is necessary; sending and receiving signals (odors,
visual, sounds, tactile)
Mating behaviors
35.14 - .15
- locating and attracting a mate
- displays (innate behaviors) or competition among males is important in mate
choice (usually female choice)
- allows identification of correct species and sex
- allows choice (usually female) of mate with best genes
- several mating systems have evolved:
- promiscuous - no strong pair bonding
- monogamous - strong pair bonding between 1 male and 1 female
- polygamous - strong bonding between 1 of one sex and several of the
opposite sex
- system that evolves is the system that maximizes reproductive success for the
individual
- requirements of feeding and protecting young
- “cheating” can benefit males or females in some circumstances (what produces
most surviving offspring for the individual)
- “anti-cheating” mechanisms have evolved (chastity plugs, repulsive odors,
“killer” sperm, etc.)
- certainty of paternity (for male) is important in the evolution of the mating
system
*How does certainty of paternity compare in animals with internal fertilization to animals
with external fertilization?
Social behaviors that space and rank group members
35.18 - .20
- dispersion (spacing) is outcome of social interactions and ______?
- clumping is positive interaction (herd, pack, school, etc.)
- increases feeding efficiency, defense against predators
- establishing territories is negative interaction, other individuals are
excluded from an area
- provides an exclusive area for feeding, breeding or shelter
- allows improved spatial learning for more efficient foraging and
escape from predators
- dominance hierarchies rank members within a group
- “pecking order” alpha to omega
- dominant individual gets access to food, mates, etc.
- lower ranking individuals submissive to alpha
- allows group to maintain more efficient functioning - hunting, defense,
raising young, etc.
- pattern that develops is compromise of energy expended to energy gained that
maximizes reproductive success
- aggressive (agonistic) behaviors are usually ritualistic (test of strength, posturing
displays, etc.)
- reconciliation behaviors (grooming, appeasement) are also common
*How does this benefit both winner and loser?
*How does this benefit members of the group?
*How could it be beneficial for a low ranking individual to cooperate within the group?
Altruistic behaviors
35.21
- behaviors that reduce an individual’s fitness (reproductive success) and
increases another individual’s fitness; selfless, self-sacrificing
- ex. alarm calls, sharing resources, protection of another
- inclusive fitness is when an individual helps related individuals that share genes
(parents for offspring and helping close relatives)
- kin selection favors altruistic behaviors that increase inclusive fitness (this
increases the number genes that an individual gets into the future)
- reciprocal altruism is selfless behaviors for non-related individuals
- something expected in return
- not common, usually in stable social groups where individuals are
recognized
8. Habitat - specific place where a species is found
- ex. shallow ponds with vegetation, open grassland prairies
34.1
9. Niche - role of species in its habitat
37.3
- how it exists and uses resources
- ex. how and when it feeds, when it is active, range of physical conditions it
tolerates
Biology 1407
Exam 4 Review Ecology Ch 35 & 36
Define the term ecology.
Why do biologists think that studying ecology is important in understanding the biology of individuals?
List the levels of organization in living organisms.
Define the term population.
How is a population of bull snakes (as a specific example) different than the bull snake species?
Define the term density and give an example. Distinguish between ecological and crude density.
Which is always larger than or equal to the other?
Define the term dispersion and distinguish between random, clumped and even.
Give some examples of each. What causes each?
Explain what a life table is and how it is expressed as a survivorship curve.
Distinguish between types I, II and III curves.
What is measured in an age and sex structure of a population?
What are pre-reproductive, primary reproductive and post-reproductive individuals?
How does this affect a populations potential for growth?
Define the term intrinsic rate of increase (also called biotic potential or r maximum) and make a graph showing
this type growth rate.
Add to this graph the growth rate of a population with ractual. At what number does the population stop
growing (given the symbol “K“)?
Clearly mark on your graph the point of maximum sustainable yield.
Why is this important to our efforts at resource management? Why is resource management important?
List the four events that will change the number of individuals in a population.
Define the term regulating factor and distinguish between density dependent and density independent
regulating factors. Give examples of each.
Describe the human growth rate during the last 500 years. What is the carrying capacity of Earth for
humans? What regulating factor(s) will slow our growth rate?
Define the term life history and tell why a population will develop a certain life history.
What is the final measure of success (also called fitness)?
List and describe the four most important traits in a life history.
Distinguish between “opportunistic” (r) and “equilibrium” (K) life histories.
Give the features of each and describe the environment where each would evolve.
Define the term animal behavior and tell how this is related to evolutionary fitness.
Define the term social behavior and give some examples. What is necessary for social behavior to develop?
What are agonistic behaviors and why are they almost always ritualistic?
What are reconciliatory behaviors and why are they important?
Describe the several mating systems that evolve and tell why a particular mating system would evolve in a
certain population.
How do cheating and certainty of paternity determine the mating system?
Why are innate displays important to mate choice - what information do they give?
How is it beneficial to females to passively accept the winning male (in a mating system where males
compete with each other for the females and females have little choice)?
Describe the behaviors that will lead to either a clumped dispersion or an even dispersion.
Describe an advantage of each.
What is a dominance hierarchy?
Why is it important to members of the population and why should a lower ranking member not fight to the
death to become a higher ranking member?
Define the term altruistic behavior and give some examples.
What is inclusive fitness and how does it lead to kin selection?
What is reciprocal altruism and why is it not very common in nature.
Why does this almost always only occur in complex stable social systems?
Define the term habitat and give examples.
Define the term niche and give examples.