Download File - Biggs` Biology

Introduction to Ecology
Ecology
A
rigorous experimental science that
requires a breadth of biological
knowledge.
 Ecologists observe nature, generate
hypotheses, manipulate
environmental variables, and
observe outcomes.
Biological Hierarchy
Global ecology- the biosphere
 Landscape ecology-energy exchanges
 Ecosystem ecology-energy flow and
chemical cycling
 Community ecology-interactions between
species
 Population ecology-changes in population
size
 Organismal ecology- organism’s structure,
physiology and behavior

Earth’s Climate Influences
 The
most significant influence on the
distribution of organisms on Earth is
climate
 Climate is composed of 4 abiotic
factors
– Temperature
– Precipitation
– Sunlight
– Wind
Macroclimate
 Seasons
are caused by variation in
sunlight intensity
Latitudinal Variation in Sunlight
Global Air Circulation and
Precipitation




Intense solar radiation
near the equation
Warm moist air rises flows
toward the poles releasing
water
Dry air descends at 30o
north and south, absorbing
moisture & rises again at
60o releasing precipitation
Movement of air due to
Earth’s rotation aids in
creating the prevailing
westerlies and the trade
winds
Bodies of Water
 Ocean
currents influence climates by
heating or cooling overlying air
masses
 Water’s high specific heat moderates
climates of nearby land
Mountains
Influence air flow and the amount of
sunlight an area receives.
Terrestrial Biomes
Biomes are
characterized by
vegetation type,
latitude; mean
temperature and
precipitation .
 Named for a major
physical or climatic
feature and for
predominant
vegetation.

Major Land Biomes
Aquatic Biomes
Determined by
depth, flow,
temperature, and
chemistry of the
overlying water.
 Photic zone- light
for photosynthesis
 Aphotic zone- little
to no light

What is Population Density?

The number of
individuals of the
same species per
unit area or
volume
– i.e. the number of
meerkats per
square kilometer.
Species Distribution
 Distribution
is a result of ecological
and evolutionary interactions
 Dispersal – the movement of
individuals from their area of origin
 Biotic factors – such as predation,
herbivory, parasites, food resources.
Patterns of Dispersion

Clumped
– Most common
pattern
– Spend much of time
in particular
microenvironment
– Associated with
mating behavior
Mark-recapture Method
One method used by ecologist to calculate
population densities
 Traps are set, captured animals are
marked with tags then released
 After a period of time a second capture is
done, researchers estimate numbers
based on the yields of marked and
unmarked individuals.
 Assumes equal probability of being
trapped –

– Animals may be wary of traps if they were
trapped once.
Counting

It is possible to count all the individuals in
a population to determine the size.
– Not practical

Count the number of individuals (oak
trees) in randomly selected plots
– Calculate the average density in the samples
– Extrapolate to estimate the population size

Estimate density from some index of
population size.
– Number of nests, tracks, etc.
Uniform
Evenly spaced
pattern of
dispersion
 May result from
direct interactions
between
individuals in
population

Random
Pattern of
dispersion with
unpredictable
spacing
 Occurs in the
absence of strong
attractions or
repulsions

Exponential & Logistc Growth
Curves
Density dependent limiting factors
Death rate rises, or birth rate falls as
population density rises.
 Example of negative feedback regulation
 Includes

–
–
–
–
–
–
Competition for resources
Territory space
Health
Predation
Toxic wastes
Intrinsic factors
Density Independent
 Birth
rate or death rate that does not
change with population density.
 Physical factors kill a similar
proportions of a local population
regardless of its density.
– Natural disasters
– Human activity
Survivorship Curves
Type I – high
death rate in post
reproductive years
 Type II – constant
mortality
throughout lifespan
 Type III- very high
early mortality, but
the few survivors
live long (stay
reproductive)

K- selected species vs. r-selected species
Body Size
Life Span
# of
Offspring
Relative
time of
reproduction
Survivorship
Curve
Growth Curve
K-selected
species
Larger
Low
mortality
Few
offspring
Late
reproduction
Type I
s- shaped
Logistic
r-selected
species
Smaller
High
mortality
Many
offspring
Early
reproduction
Type III
Boom and bust
Exponential growth
Factors that affect Population Size

Abiotic Factors
– Sunlight & temperature
– Preciptation/ water
– Soil/ nutrients

Biotic Factors
– Prey (food)
– Competitors
– Predators, parasites,
disease

Intrinsic factors
– Adaptations