Transcript Intro to ecology

Chapters 51-56
INTRO TO ECOLOGY
1
What is ecology?
Scientific study of interactions
between organisms and their
environment
It starts at the level of individual, then
population, then community
(does NOT deal with the cellular level)
2
Biogeography
Study of past and
present distribution of
individual species
Ethology
Study of animal behavior
(think pillbug lab!)
Fixed Action Pattern 
instinctive behavioral
sequence; one of the few
types of behaviors which
was thought to be "hardwired" and instinctive
3
 The branch of ecology
that focuses on the
evolutionary causes of
variation in behavior
among populations and
species.
 It is concerned with the
adaptiveness of behavior,
the ultimate questions of
WHY animals behave as
they do, rather than the
proximate questions of
how they behave.
Behavioral
Ecology
4
 Dominance hierarchy arises
when members of a social
group interact, often
aggressively, to create a
ranking system.
Dominance Hierarchy
 In social living groups,
members are likely to
compete for access to
limited resources and mating
opportunities.
 Rather than fight each time
they meet, relative
relationships are formed
between members of the
same sex. These repetitive
interactions lead to the
creation of a social order that
is subject to change each
time a dominant animal is
challenged by a subordinate
one.
5
Behavioral Biology- terminology
Foraging – looking for food
Habituation – a simple type of learning where an animal loses sensitivity
to unimportant stimuli; this can increase fitness by allowing an animals
nervous systems to focus on the important stuff
Imprinting – also called attachment; learning that occurs during a specific
time period and is generally irreversible; babies can imprint on whoever
they think is their “mother” - ex. baby duckling following human; this bond
usually lasts a lifetime
Migrations – long-distance regular movements often involving round trips
each year
Courtship – behavior patterns that lead up to mating; often consists of a
series of displays by one or both partners
Pheromones - chemical signals commonly used by mammals and insects
in reproductive behavior to attract mates and to trigger specific courtship
behaviors; ex. Traveling behavior of ants and social/hive bees use
pheromones to maintain order of the colony
6
Conditioning
Many animals can learn to associate
one stimulus with another
Classical conditioning  learning to associate an
arbitrary stimulus with a reward or punishment
Pavlov’s dog is a good example:
Ivan Pavlov exposed dogs to a bell ringing and at the same time
sprayed their mouths with powdered meat, causing them to
salivate.
Soon, the dogs would salivate after hearing the bell, even if they
were not getting any powdered meat.
Operant conditioning this is called trial-and-error learning—an
animal learns to associate one of its own behaviors with a reward or a
punishment and tends to repeat or avoid that behavior. Ex. if a dog sits,
its gets a treat; a predator associates potential prey with painful
experiences and then modifies its behavior accordingly
7
Altruistic Behavior and Kin
Selection
Altruism – behavior that
reduces an individuals fitness
but increases the fitness of the
recipient; genes enhance the
survival of themselves by
directing the organism to assist
others who share those same
genes; people are more likely to
help relatives, even if it means
putting themselves at risk
MOST behavior is selfish and
NOT altruistic
8
Darwinian Fitness
Recall that Darwinian Fitness is measured as the number of
fertile individuals that are left in the next generation.
9
Kinesis vs. Taxis
KINESIS is a change in activity or movement in response
to a stimulus but the behavior is RANDOM. For example,
a light goes on and bugs scatter randomly to the dark.
TAXIS is movement toward or away from a stimulus.
For example, bugs moving towards a food source or away
from a predator.
10
Environment-two components
Abiotic
Biotic
 Nonliving
 Living organisms
 Examples:
 Temperature
 Light
 Water
 Wind
 Rock/Soil
 Fire/Flood
 Symbiotic relationships
(predation/ mutualism/ etc)
 Disease
11
Levels of Organization
MOST inclusive to LEAST inclusive:
Biosphere  Ecosystem  Community  Population  Individual
Population: Group of individuals of single species that
occupies the same geographic area
Community: All of the organisms of all of the species that
exist in a certain area
Ecosystem: all the biotic AND abiotic factors that exist in a
certain area
Biosphere: Global Ecosystem
**Ecology does NOT deal with organisms on the
CELLULAR level.**
12
Biogeography/Distribution
 Biotic factors affect distribution of organisms
(competition, predation, symbiosis, disease)
 Abiotic factors also affect distribution
(temp, light, etc as above)
 ** Temperature has the greatest influence on the
metabolic rate of plants/ animals
 Distribution also affected by habitat selection
(How organisms select habitat is not understood)
 Photic/Aphotic zones of ocean
13
PHOTIC  region of the
aquatic biomes where light
can penetrate; autotrophs live
here
- Main autotroph =
Phytoplankton
(PRODUCERphotosynthesis!)
- Zooplankton (Primary
Consumer) eat
Phytoplankton
APHOTIC  region of aquatic
biome where light CANNOT
penetrate
Photic vs.
Aphotic Zones
Photoperiod  the period of
time each day during which
an organism receives light;
also known as day length.
14
Estuary
An estuary is the tidal mouth of a large river, where
the tide meets the stream.
15
Biomes
Tropical Forests –
Found near the equator so it gets a
constant amount of sunlight/
temperature; lots of rain; huge
diversity of species – both plant
and animal; many of our medicines
come from plants in the rainforest
Savanna –
Tropical grasslands with
scattered trees; have both rainy
and dry seasons; many times will
have large animals grazing on the
grasses; fires are common here
DesertLow and unpredictable
precipitation, may be hot or cold
depending on location; animals here
have adaptations to deal with the dry
conditions
16
Biomes
Chaparral –
Common along
coastlines in midlatitudes and have
mild, rainy winters
and hot, dry
summers; dense and
spiny evergreen
shrubs are the
dominant plantlife
Temperate Grasslands –
Maintained by fire, seasonal drought, and grazing by
large animals; soils are deep and rich in nutrients
Temperate Deciduous
Forests –
Characterized by broadleaved deciduous trees;
have enough moisture to
support the growth of these
big trees; trees lose their
leaves before winter;
respond to different
photoperiods
17
Biomes
Coniferous Forests (Taiga) –
Characterized by harsh winters and
heavy snowfall; coniferous trees grow
in dense, uniform areas; SHORTEST
growing season
ALL terrestrial biomes show
VERTICAL STRATIFICATION.
Tundra –
Northernmost limit of plant
growth; characterized by dwarf
and mat-like vegetation
The TWO major factors in determining the
distribution of organisms (or in delimiting biomes):
Poles  Temperature
Equator  Precipitation (Water)
18
Vertical Layering (Stratification)
 Vertical layering of a habitat or the arrangement of vegetation in
layers.
 It classifies the layers of vegetation largely according to the different
heights to which their plants grow.
 The individual layers are inhabited by different animal and plant
communities.
 Canopy  the canopy of the tropical forest is the top layer
covering the layers below
 Permafrost  found in the tundra; permanently frozen stratum
that lies under ground
19
Population Density
Birth and Death Rates
 In order to calculate change in population, you can just
do birth-death rates. Let’s try a problem:
SAMPLE  A population of groundhogs has an annual per
capita birth rate of 0.08 and a per capita death rate of 0.05.
Estimate the number of individuals added to (or lost from) a
population of 100 individuals in one year.
0.08 – 0.05 = 0.03 = 3%
.03 x 100 = 3 individuals added to the population
20
Population Density
Birth and Death Rates
 Practice Problems:
A population of squirrels has an annual per capita birth
rate of 0.05 and a per capita death rate of 0.07.
Estimate the number of individuals added to (or lost
from) a population of 500 individuals in one year.
2. A population of rabbits has an annual per capita birth
rate of 0.09 and a per capita death rate of 0.05.
Estimate the number of individuals added to (or lost
from) a population of 1000 individuals in one year.
1.
21
Population Density
Birth and Death Rates - ANSWERS
 Practice Problems:
1. A population of squirrels has an annual per capita birth rate of 0.05
and a per capita death rate of 0.07. Estimate the number of
individuals added to (or lost from) a population of 500 individuals in
one year.
0.05 – 0.07 = -0.02
500 x -0.02 = -10 individuals
So 10 individuals lost each year
2. A population of rabbits has an annual per capita birth rate of 0.09
and a per capita death rate of 0.05. Estimate the number of
individuals added to (or lost from) a population of 1000 individuals
in one year.
0.09 – 0.05 = .04
1000 x 0.04 = 40 individuals
So 40 individuals added each year
22
Population Density
Mark and Recapture
In order to estimate the population size of a group of organisms,
scientists can use the Mark and Recapture method. The basic
process is:
- Capture as many individuals as you can, count them, and
mark them
- A certain amount of time later, recapture as many
individuals as you can and count them. Also, count how
many of those were marked.
- Calculate the population size using the following equation:
N = sn
N = population size
x
s = # marked in the 1st sampling
n = total # captured in the 2nd sampling
x = # marked in 2nd sampling
23
Mark and Recapture Method
Practice Problems
1. If we capture 100 birds, mark them, then release them,
and we come back the next day and capture 120
more…but 20 had already been marked, what is the
estimated population?
2. We caught, marked and released 200 butterflies. The
next day, we came back and caught 160. Of those 160, 40
were marked. What is the estimated population size?
N = sn N = population size
x s = # marked in the 1st sampling
n = total # captured in the 2nd sampling
x = # marked in 2nd sampling
24
Mark and Recapture Method
Practice Problems - ANSWERS
1. If we capture 100 birds, mark them, then release them, and we
come back the next day and capture 120 more…but 20 had
already been marked, what is the estimated population?
N = (sn)/x
N=
(100 x 120) / 20
(12000)/20
600
2. We caught, marked and released 200 butterflies. The next day,
we came back and caught 160. Of those 160, 40 were marked.
What is the estimated population size?
N=
(200 x 160) / 40
N = sn N = population size
x s = # marked in the 1st sampling
(32000)/40
n = total # captured in the 2nd
sampling
800
x = # marked in 2nd sampling
25
Survivorship Curves
A survivorship curve shows the
number of individuals, or proportion,
still alive in a population at each
age. There are 3 types:
- Type I  low mortality during early
and middle age and a rapid increase
in old age; typical in populations that
produce relatively few offspring and
provide parental care; Ex. Humans
who live in developed countries
- Type II  death rate is relatively
constant throughout a lifespan
- Type III  typical of populations
that produce many offspring, most
of which die off rapidly; the few
offspring that survive are likely to
reach adulthood
This kind of curve is impossible
– it can’t go down and then go
back up
26
Population
Growth
Exponential Population
growth model
 Population growth under
ideal conditions
 Assumes unlimited
resources (does NOT take
into consideration
carrying capacity)
 “J” shaped curve
The human population shows
this kind of growth due to:
- improved sanitation
- vaccinations/ pesticides
- better nutrition
27
Intrinsic Rate of Increase
 The rate at which a population increases in size if there are no
density-dependent forces regulating the population is known
as the intrinsic rate of increase.
 The theoretical maximum rate of increase of a population per
individual. The concept is commonly used in insect
population biology to determine how environmental factors
affect the rate at which pest populations increase.
 J shaped curve
28
Population Growth
Logistic population
growth model
N – population size
K – carrying capacity
•Does not assume unlimited
resources (like exponential); takes
into consideration carrying
capacity
•Incorporates effect of population
density on rate of increase
•“S” shaped curve
•Carrying capacity= maximum
population size a particular
environment can support with the
available resources at particular
time w/ NO degradation of habitat
• “K”=carrying capacity
The LOGISTIC EQUATION says
• Factors include: energy,
shelter, soil nutrition, water, that as N approaches K, the
nesting sites, etc.
GROWTH RATE will decrease
and approach zero
29
Selection for life history traits
 K - selection (DENSITY DEPENDENT)
 Maximize population size in a population living near carrying
capacity
 Few offspring, parental care; Ex. humans
 Humans
 S-shaped curve
 R - selection (DENSITY INDEPENDENT)
ALL
POPULATIONS
of the SAME
SPECIE show
either R- or Kselection
 Found in un-crowded environments – so the population is
lower than carrying capacity and there is little competition;
can occur in disturbed habitats
 The RATE OF INCREASE is HIGH in the population
 High repro. rate ; produce many/ small offspring; high
mortality of offspring; LITTLE parental care ; Ex. frogs
 J-shaped curve
30
Negative feedback:
The death rate increases as the population
density increases, so this prevents unlimited
population growth
This affects DENSITY- DEPENDENT (S-curve; logistic
model) populations because they often fall close to the
carrying capacity. DENSITY–INDEPENDENT populations
(J-curve; exponential model) are NOT affected by negativefeedback.
31
Ecology concepts
 Community- assemblage of populations in an
area or habitat
 Ecological niche- an organisms interaction
with the biotic and abiotic resources in the
environment
 How is “fits into” an ecosystem (what is its “job”)
 Competitive Exclusion Principle no two
species can occupy the same niche
32
Effect of Fire on Communities

Fire can have an integral role in recycling dead
plant matter and allowing those nutrients to
become more available. Many ecosystems,
particularly prairie, savanna, chaparral and
coniferous forests, have evolved with fire as a
contributor to habitat vitality and renewal. Many
plant species in fire-affected environments require
fire to germinate, establish, or to reproduce.

Fire suppression can lead to the build-up of
flammable debris and the creation of less frequent
but much larger and more destructive wildfires.

Recent ecological research has shown that fire is
an integral component in the function and
biodiversity of many natural habitats, and that the
organisms within these communities have
adapted to withstand, and even to exploit, natural
wildfire. More generally, fire is now regarded as a
'natural disturbance', similar to flooding, windstorms, and landslides, that has driven the
evolution of species and controls the
characteristics of ecosystems.
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Succession
Primary vs.
Secondary
Succession
34
Symbiosis
Predation- predator/prey; can lead
to adaptations (coloration etc);
benefits one organism, harms the
other
Parasitism - benefits one organism
(parasite) and harms the other (host); the
parasite lives in or on the host; Ex. can
be in animals (tapeworms) OR can be in
plants  smaller plants live on larger
trees and take the nutrients away from
the larger trees (smaller plant gets the
nutrients, bigger tree is harmed b/c it is
losing nutrients)
35
Mutualism- benefits both species;
Ex. Oxpecker (bird) and the
rhinoceros or zebra  the bird
lands on rhinos or zebras and
eat ticks and other parasites
that live on their skin. The birds
get food and the beasts get pest
control
Commensalism- interaction
benefits one species; does not
affect the other; Ex. barnacles
living on a whale  barnacles
get a habitat where nutrients
are available from the water,
but this does not help or hinder
the whale
36
Coloration and
Mimicry
Mullerian
Mimicry
Coloration –
Animals that are typically prey can sometimes use coloration as a defense. If
the organism has colorations that help it blend into the background, it is called
cryptic coloration. If they are brightly colored and stand out to ward their
predators that they are harmful, that is called aposematic coloration.
Mimicry –
Batesian mimicry  harmless or goodtasting species mimic a harmful or gross
tasting one so that the predators think it will
not be good to eat
Mullerian mimicry  two animals that are
BOTH harmful mimic each other so that
there are more of the “bad” organisms in the
community – this way the predators learn
faster not to eat them
In order for mimicry to work, both
organisms have to be in the SAME
geographic area
Cryptic Coloration
37
Food
Chains
All food chains must start with a PRODUCER (autotroph).
The organism that eats the producer is called the PRIMARY
CONSUMER. If they only eat plants, they are also called
herbivores.
An animal that eats a primary consumer is called a SECONDARY
CONSUMER. If that animal eats only meat, they are called a
carnivore.
If an animal eats both plants and meat, they are omnivores.
The Dynamic Stability Hypothesis says that long food chains are less
stable than short chains, and population fluctuation magnified at higher
levels. Remember, less than 20% of energy is passed from one
trophic level to the next, so food chains are kept relatively SHORT.
38
 Food chain- transfer of food between trophic levels (level of
consumption); only LESS THAN 20% of energy is passed on to
next level (usually about 10%)
 TROPHIC EFFICIENCY  % of production transferred from
one level to the next
 Food web - summarizes trophic relationships in a community ;
more realistic than a food chain; MAKE SURE YOU ARE ABLE
TO IDENTIFY WHERE THE PRODUCER IS AND WHERE THE
CONCENTRATION OF TOXINS WOULD BE HIGHEST (at the
highest consumer!!)
39
Introduced Species
 Definition = a species living outside its native
distributional range; humans put the
organism there either on purpose or
accidently
 Effects introduced species can have:
 Competes with native species for resources
 Displaces native species
 Preys on native species
 Reduces biodiversity
 Only about 10% of introduced species
actually survive and thrive in the new location
 This is called the Ten’s Rule
40
Keystone Species

A keystone species is a
species that has a
disproportionately large effect
on its environment relative to
its abundance. Such species
are described as playing a
critical role in maintaining the
structure of an ecological
community, affecting many
other organisms in an
ecosystem and helping to
determine the types and
numbers of various other
species in the community.

An ecosystem may experience
a dramatic shift if a keystone
species is removed, even
though that species was a
small part of the ecosystem by
measures of biomass or
productivity.
41
Primary Production in Ecosystems
 Energy will flow NOT cycle thru
ecosystem
 Comes in as light energy and leaves
as heat
 Production efficiency
 Fraction of food energy NOT used
for respiration
 Herbivores consume only a fraction
of the plant material produced; they
can’t digest all they eat; and much of
that energy is used for respiration
 Trophic efficiency
 Percentage of production
transferred from one trophic level to
the next
 Usually between 10-20%
42
Primary Production in Ecosystems
 Gross-GPP, is the total amount of light
energy converted to chemical energy…the
organisms photosynthetic output
 Net-NPP, is the net amount of primary
production after the costs of plant respiration
are included.
 Therefore, NPP = GPP - R
43
Humans
 Humans show K- selection (density dependent), show a type
I survivorship curve, have a relatively small family size, and
show a relatively even age structure
 Humans- widespread agents of community disturbance
 Reduces species diversity
 Humans are the BIGGEST THREAT TO BIODIVERSITY
4 major threats to
biodiversity:
1. Habitat destruction
2. Introduced species
3. Overexploitation
(overharvesting)
4. Disruption of food
chains
44
Humans Impact the Biosphere in
several ways:
 Agriculture (interfering with nutrient recycling)
 Eutrophication
 Acid Precipitation
 Toxic compounds (DDT, PCM)
 CO2 (greenhouse, global warming)
 Habitat destruction
45
Eutrophication
Eutrophication is characterized by an
abundant accumulation of nutrients
(sewage, factory wastes, fertilizer, etc)
that causes a dense growth of algae and
cyanobacteria (blooms!). The presence
of these organisms (and their
respiration) leads to an oxygen shortage
in the rest of the water, and that lack of
O2 kills off many fish and animals.
46
Acid Rain
Acid rain is defined as
rain, snow, or fog with a
pH less than 5.6.
Burning wood and coal
releases oxides of sulfur
and nitrogen which can
form nitric acid in the
atmosphere. These
acids return to the
earth in acid rain, which
can change soil
chemistry. This change
can lead to damage in
forests and also lakes.
47
Toxic Compounds
Many toxic chemicals dumped into ecosystems
are non-biodegradable; some may become
more harmful as they react with other
environmental factors. Organisms absorb these
toxins from food and water and may retain them
within their tissues. Chlorinated hydrocarbons,
such as DDT, and polychlorinated biphenyls, or
PCBs, have been implicated in endocrine
system problems in many animal species. In a
process known as biological magnification, the
concentration of such compounds increases in
each successive link of the food chain.
48
The phenomenon
whereby the earth's
atmosphere traps
solar radiation,
caused by the
presence in the
atmosphere of gases
such as carbon
dioxide, water vapor,
and methane that
allow incoming
sunlight to pass
through but absorb
heat radiated back
from the earth's
surface.
The Greenhouse Effect
CO2 is the MAIN
greenhouse gas.
49
Global Warming
Global Warming is an
increase in the earth's
average atmospheric
temperature that causes
corresponding changes in
climate. This may result from
the greenhouse effect.
50