Download Ecology Lecture IV

Ecology Standards:
6c ~ Students know how fluctuations in
population size in an ecosystem are
determined by the relative rates of
birth, immigration, emigration, and
death.
Biological Interactions
How species interact with each other and with the
world around them
Habitat & Niche
 The
habitat of an
organism is considered
Leopards are graceful and powerful
big cats closely related to lions, tigers,
and jaguars. They live in sub-Saharan
Africa, northeast Africa, Central Asia,
India, and China. However, many of
their populations are endangered,
especially outside of Africa. (National
Geographic)
all of the biotic and
abiotic factors where
an organism lives
Habitat & Niche
 The
ecological niche
of a species is made
up of all the physical,
chemical, and
biological
factors
that
a
Native to the Central Asian mountains,
the snow leopard is a rare sight, with species needs to
only about 6,000 left in the wild. They
survive, stay healthy,
are hunted for their beautiful, warm
fur and for their organs, which are
used in traditional Chinese medicine. and reproduce
(National Geographic)
Habitat & Niche
Think of a habitat as where a species lives and
the niche as how it lives within its habitat
 A niche includes:

Food – type of food, how it competes for food, and
where it finds its food
 Abiotic conditions – air temp., amount of water,
etc.
 Behavior – the time of day a species is active as
well as where and when a species reproduces

Habitat & Competition

When two species live in the same
habitat it is possible that they may
require the same resources


One species will always be better
adapted to obtain a resource over
another
The competitive exclusion
principle states that when two
species compete for the same
resources, one will “win” and the
other will be ‘forced’ into a new
niche or become extinct
Habitat & Competition

When two or more species compete for resources
(competitive exclusion) it can have 3 Effects:



Extinction – one species puts so much pressure on the
other that it dies out
Niche partitioning – the two species could occupy
different niches near each other not overlapping
Evolutionary response – one species may evolve or be
‘selected for’ different traits and evolve away from the
original form
Habitat & Competition

An ecological equivalent
would be a case where two
species occupy the same
niche in different parts of
the world
Community Interactions

Competition happens when
two organisms fight for
similar resources such as
food, space, or water
Interspecific competition –
happens when two different
species compete
 Intraspecific competition –
occurs when the same species
compete

Community Interactions

Predation – the process
by which one organism
captures and eats another
organism
Community Interactions

Symbiosis – an interaction between two
or more organisms that live in direct
contact with one another


(Sym = same) (Bio = life) (Sis = together)
There are 3 Types of Symbiosis:
Mutualism
 Commensalism
 Parasitism

Mutualism

Mutualism – a
symbiotic relationship
where both species
benefit from the
interaction
A cleaner shrimp reaches into a moray eel's mouth.
The shrimp uses its claws to pick stuff off the eel's
body. That can include dead skin, tiny pieces of
food, and even little creatures that can hurt the fish.
(National Geographic)
Commensalism

Commensalism – an
interaction between
organisms where one
species benefits and the
other does not benefit
nor is it harmed
The clown fish swims among the stinging
tentacles of the sea anemone for protection
and safety. The sea anemone does not
benefit from this relationship nor is it
harmed. The clown fish is safe in its
anemone home!
Parasitism

Parasitism – a
relationship where
one organism
benefits while the
other is harmed

Parasites keep their
host alive for days
or even years while
predation kills
immediately
Organism Population
One of the main goals of all living things is to
reproduce
 Studying organism population distribution and
growth is an important part of Ecology
 Population density – is a measurement of

the number of individuals living in a defined
space
Organism Population

Organism populations have varying
types of population dispersion
(aka) distribution
Clumped – living close together
 Uniform – living at regular intervals

in relation to one another
 Random – living in random places
and distances from one another
 Each
of these types has its own
advantages and disadvantages
Organism Population
 Population
Growth and the Four Factors:
 Migration
(two types)
 Immigration
– moving “in to” an area
 Emigration – moving “out of” an area
 Birth
& Death
 Birth
rates – new organisms born cause an
increase in population
 Death rates – organisms dying cause a
population to decrease
Organism Population
Population
Change

=
Births
+
Immigration
–
Deaths
+
Emigration
To calculate an overall population increase
or decrease, you must know all four factors
Population Growth

There are Two Main Types:

Exponential – a population
increases quickly over a
short period of time
 Logistic – a population
begins with slow growth
followed by rapid growth
before leveling off or slower
growth
A
carrying capacity occurs
here
Limits to Growth
Most populations have a
limit to how large they
can get
 A limiting factor is any
factor that causes
population growth to
decrease or stop
 A carrying capacity is the
maximum number of
individuals a given area
can support

Carrying capacity
Limits to Growth

There are Two Types of Limiting Factors:

Density-dependent – affects a population
differently depending on the size of the population
 Example:
a disease can have a greater effect on a larger
population versus a small population that is spread out
(diseases, predation, competition, & parasitism)

Density-independent – affects a population in
similar ways regardless of its size
 Example:
an earthquake will happen regardless of the
size of the population of groundhogs in a certain area
(natural disasters, seasons, & unusual weather)
Ecological Succession
Occasionally an
ecosystem suffers a
tragic event that kills all
life
 Succession – the
sequence of biotic
changes that regenerate
a damaged community
or a ‘new’ area

Ecological Succession

Primary succession occurs when a new area
is available for colonization of species

The pioneer species is the first species to colonize
an area of primary succession
 Mosses,
lichens, and other primitive plants take root into
rock and break it down over a long period of time into
the first soil
Ecological Succession

Secondary succession –
regenerates a community
quicker than primary and
usually follows a natural
disaster
Yet, another reason not to smoke
Sample Test Question

Many lakes in the U.S. have received large
amounts of nutrients, such as nitrogen and
phosphorus, as a result of pollution from
farms and industry. This pollution causes
rapid and massive increases in some lakes’
algae population. This gradually depletes
oxygen supply, killing many organisms.
What is the most logical explanation for the
rapid growth of algae?
Sample Test Question
(answers)
A) The increased nutrients led
many organisms to emigrate
 B) The increased nutrients
supported the population growth
of algae
 C) The increased nutrients allowed
algae to outcompete other species
 D) The increased nutrients caused
algae to immigrate
