Chapter 6: Communities
Download
Report
Transcript Chapter 6: Communities
Chapter 8
Populations
Population Properties
The numbers or population of an
organism is limited by their
environment
Population- all the members of a species
living in the same area at the same time
Ex: all the oak trees in Houston County
Properties
Can be described by:
Population size
Population Density
Patterns of dispersion
Demographics
Population growth
Limits on population growth
Terms to Know
Population size- number of individuals present
living in a defined area
Population Density- number of individuals in a
population per unit area
Population dispersion or distribution- the spatial
arrangement of organisms within a particular
area
Sex ratio- proportion of males to females
Distribution Patterns
Populations may be distributed in different
ways:
1. Random- individuals located haphazardly in
no particular pattern (minimal interaction)
Individuals are independent of others
Can occur when resources are found
throughout an area
Distributions
2. UNIFORM DISTRIBUTION
Individuals are evenly spaced, same distance
apart
Can occur when individuals hold territories or
compete for space
Ex: plants in the desert need certain amount of
“root” space to get water they need
Distributions
3. CLUMPED DISTRIBUTION
Most common in nature
Organisms arrange themselves according to
the availability of resources
Organisms interact and are attracted to
certain areas
Ex: Bees and flowering plants, breeding
pools, humans to urban areas
Distribution Patterns
Age Distribution/Structure
Describes the relative numbers of organisms
of each age within a population
Can make predictions based on age structure
Ex: Population past reproductive age will
decline over time
Population pre-age or at age of reproductionwill likely increase
Even age distribution – remain stable
Age Structure Diagrams
Survivorship: percent of members likely
to survive
Growth rate: birth & death rates, change
in size
Growth rate= birth rate – death rate
Rate can be zero (no increase); negative
(decrease); or positive (exceeds death
rate)
Age Structure Diagram
Graphs
Survivorship Factors
Determined by 4 factors:
1.) Births (natality)
2.) Deaths (mortality)
3.) Immigration – arrival on individuals outside the
population
4.) Emigration – departure of individual from the
population
Survivorship Types
K-selected
r-selected
Devote large amounts of
energy and resources to
caring for a few
offspring
Devote their energy and
resources to producing
as many offspring as
possible in a short time
Tend to stabilize over
time at or near their
Carrying Capacity
Survivorship is left to
chance
K is abbreviation for
Carrying Capacity
Exponential Growth
Exponential Growth
Occurs when a
population or
anything else,
increases by a fixed
percentage each year
Occurs when pop. has
plenty of food, space
and limited
competition or
predators
Limiting Factors
Anything that Restrain population growth
Carrying Capacity- the maximum pop. size of
a species that a given environment can
sustain
Carrying Capacity Graph
r-selected vs K-selected
Exponential vs Logistic
Logistic Growth (Curve)
(Carrying Capicity)
limiting factors =
environmental
resistance
Space, food,
water, shelter,
disease,
predators, temp.
mates/breeding
sites
Plants: sunlight,
moisture, soil
Aquatic: salinity,
sunlight, temp,
dissolved
oxygen, and
pollutants
Limits to Pop. Growth
Density Dependent:
depends on size
of the population
Increases and
decreases with
population
density
Can help find mates,
but increases:
Competition
Predation
Disease and
Parasitism
Limits to Pop. Growth
Density Independent
Examples:
Limiting factors that
affect the population
regardless of size
(density)
Climate/Temperat
ure extremes
Can eliminate large #’s
of individuals without
regard to their density
Natural/Catastrop
hic events or
disasters
Human Activity
Chapter 8: Species
Interactions
And Community Ecology
Standard 3 - Communities
CLE3255.3.1 – Ecological niches and various
habitats
CLE3255.3.2 – Species interactions, predation
competition = symbiotic relationships
Organisms Niche
Includes species habitat use, its role in the
community, consumption of foods, use of
resources, role in food chain/food web, and
it’s interactions with other organisms
Summary of everything an organism does in
its environment
Types of Niches
Fundamental Niche
Realized Niche
The full niche of a
species
Plays only a part of its
(species) role
No competitors
Forced to use fewer resources
due to competition or other
species interactions
Fulfills all its roles or
uses all resources it
can and capable of
using
Competitors restrict what an
organism can do or what
resources it can use
Chart – Fig. 6.2, pg. 143
Species Relationships
When 2 organisms living in close association
with each other interact = Symbiotic
relationship
In symbiosis, at least one of the organisms
usually benefits from the relationship
Species Interactions
Types:
Competition
Predation
Parasitism
Herbivory
Mutualism
Commensalism/Amensalism
Competition
Occurs when more than one species is
seeking or attempting to use the same
limited resource
Can take place in 2 ways:
Intraspecific Competition – competition
among members of the same species
Interspecific Competition – competition
among members of two or more different
species
Consequences of
Competition
Competition Exclusion –
when one species excludes
another species from
resource use entirely
Species Coexistence –
when neither species fully
excludes the other, live in
equilibrium;
*use resources at different
times of the day or
different levels
Resource Partitioning – the
species partition or divide the
resources they use in common
Character displacement –
evolve physical characteristics
that reflect their portion of
resource use, natural selection;
*Ex: birds eat same type of seed
– one eats the smaller, the other
the larger seeds
Larger seeds = bigger beak;
Smaller seeds = smaller beak
(Darwin’s Finches)
Predation
Process in which a (predator) hunts, captures, kills,
and eats another organism (prey);
*one benefits/one harmed
The primary organization forces and influence in
community ecology
These interactions structure/influence food
chains/webs, community make up, numbers and
abundance of the predator and prey; creates cycles
in populations
Predation
Adaptations of Predation
Camouflage: blending in with environment
Warning coloration: black stripes or red, orange
and yellow
Mimicry: imitates another organisms warning
coloration
Protective covering: quills, shells, exoskeleton
Odors/Poisons/Inks: skunks, snakes, octopus
Flying
Parasitism
Relationship in which one organism (parasite)
depends on another (host) for nourishment, while
doing the host harm
Some parasites cause little harm, while others kill
Some parasites live in close contact with the host;
ticks, tapeworm, and lampreys
Others are free-living and come into contact with
the host infrequently
Herbivory
* When animals feed on the tissues of plants
Insects that feed on plants are the most
widespread type
Some plants recruit animals as allies to help
in defense
Mutualism
Relationship in which 2 or more
species benefits from the interaction
with each other
Bacteria in our intestines
Acacia trees and ants – trees provide
shelter, the ants defend and protect the
trees
Commensalism and
Amensalism
Commensalism: one species benefits, the other is
neither harmed or helped (unaffected);
*Sharks and remora’s: remora’s attach to sharks and
feed on scraps of food; clown fish/sea anemome
Amensalism: one species is harmed and the other
is neither harmed or helped (unaffected);
*Ex: black walnut tree that secretes chemical that
kills neighboring plants, penicillin/bacteria
Energy/Biomass
Food webs: show relationships and energy flow
Keystone species: strong impact on community;
secondary and tertiary consumers
Community that resists change and remains stable;
shows resistance
A community that changes in response to
disturbance then returns to original state; shows
resilience