Download Ecology

Population Ecology
Population:
Group of interbreeding
members of the same
species that exist in a
specified area
Ecology:
Interactions among
organisms and between
organisms and the
environment
Population Demographics
Population size: total number of individuals in
a population
Population density: number of individuals per
unit area or volume
Population distribution: spacing of members
within a population in a specific area
Boundary of a population: natural or arbitrary
Patterns of Distribution
Clumped:
Attraction
Members of a
population group in
patches/ most common
Unequal distribution of
resources
Social
Reduce risk of
predation
Uniform: Active
repulsion
Even distribution
Competition for limited
resources
Plants competing for
resources/ Allelopathy
Territorial behavior in
animals
Random: minimal
influence
Uniform distribution
of resources
No pattern
Rare because of
social interactions
and varying habitats
Population Size
Plot Sampling
Uniform conditions
Mostly non mobile
species
Used to estimate population size in a defined area
based on direct counts in small portions of the area
Mark - Release - Recapture
Involves marking a number of individuals in a natural
population, returning them to that population
This technique is commonly used by fish and wildlife
managers to estimate population sizes before fishing
or hunting seasons
Why does the size of
a population
change?
 Birth and immigration
 Death and emigration
Interactions between
biotic and abiotic factors
cause variations in
population size
Factors Affecting Population Growth
Density-dependent factors:
Intraspecific competition (food, territory and
other resources), predation, diseases
Density-independent factors:
Weather changes, fires, habitat
destruction,….
Community Ecology
Community
All populations existing together in one
habitat with the potential to interact
Community Structure
Species Diversity:
Species richness :
number of species in a
community
Relative abundance:
proportional
representation of a
species in a community
Interspecific interactions: members of different
species/ could be helpful or harmful
Symbiosis
“Living together”
Can be a commensal, mutualistic, or
parasitic relationship
Commensalism
One species benefits without affecting the other
Barnacles and whales
Epiphytes
Mutualism
Both species benefit
Interspecific Competition
Similar ecological niches
Shared resources are limited
Adversely affects both species
Predation
One species (the predator) captures, kills, and
eats another species (the prey)
 Abundance of prey
affects abundance of
predators
 Number of preys
killed affected by
time it takes the
predator to eat the
prey
 Selection pressure
Defensive Adaptations of Prey
Hard or sharp parts that make prey
difficult to eat
Chemicals that taste bad or sicken
predators
Warning coloration that predators learn to
avoid, such as the black and yellow stripes
of stinging wasps and bees
Mimicry
A species evolves
traits that make it
more similar in
appearance to
another species
Camouflage
Coloration or body
form that helps an
organism blend in
with its
surrounding and
escape predation
or become a better
predator
Herbivory
An animal feeds on plant parts
Two types of defenses against herbivory
Withstand and recover quickly
Traits such as spines, tough leaves, or toxins that
deter herbivory
Plant defenses favor adaptations in herbivores
Example: Koalas have special enzymes to break
down toxins in eucalyptus
Parasites and Their Hosts
Parasitism
One species (the
parasite) feeds on
another (the host),
without immediately
killing it
Endoparasites
Ectoparasites
Parasitoids
An insect that lays eggs in another insect, and
whose young devour their host from the inside
Biological pest control
Brood parasitism
One egg-laying
species benefits
by having
another egglaying species
rear their
offspring
Ants and Alcon blue butterfly
How Do Communities
Change Over Time?
Primary succession
(barren habitat)
Pioneer species
(mosses and lichens),
colonizing a new habitat
Secondary succession
(a new community in a
disturbed area)
Physical Disturbance of the Environment
Adapted species
Indicator species
How Can A Single Species Alter
Community Structure?
Keystone species
A species that has a disproportionately large
effect on community structure
Loss or addition of even one species
(keystone species) may destabilize the number
and abundances of species in a community
Sea stars feed on
mussels
Mussels take over
when sea stars are
absent
Reduction in
species diversity
Exotic species
A species that evolved in one community and
later became established in a different one
Can dramatically alter a natural community
More than 4,500 exotic species have become
established in the United States
www.invasivespeciesinfo.gov
Ecosystems
Ecosystem
 A community
of organisms together with the
nonliving components of their environment
(desert, coral reefs, prairies, tropical forests)
 Described
as open system as it requires
continuous input of energy
 Organisms
and their environment interact
through a one-way flow of energy and
cycling of nutrients
Producers/ (Autotrophs)
Organisms that obtain energy directly from the
environment and carbon from inorganic sources to build
organic compounds
Photoautotrophs and chemoautotrophs
Primary production
 Rate at which producers capture and store energy
 Varies by ecosystem, season (day length, amount
of rain,…), and nutrient availability and type of
producer
Consumers/ obtain energy and carbon by feeding on
producers and one another
Herbivores
(plants)
Carnivores
(animal flesh)
Parasites
(tissues of a living host)
Omnivores
(plants and animals)
Detritivores
(detritus, decaying organic matter)/earthworms
Decomposers
Fungi
(waste and remains)/ Bacteria, Archaea and
Trophic Structure
Energy transfer in
terms of who eats
whom
Hierarchy of feeding
relationships in an
ecosystem
Number of levels?
Food Chain
 Describes
how
energy and
materials are
transferred from
one organism to
another
 Trophic level:
position of an
organism in a
food chain
Food Web
Grazing food chain, Detrital food chain
Human Effects on the Biosphere
Extinct species
Endangered species: a species that faces
extinction in all or part of its range
Threatened species: a species that is likely to
become endangered in the near future
Endemic species: a species that is confined to
the area where it evolved
Causes of Species Decline
 Overharvesting
 Habitat alteration, often by humans
Deliberate or accidental
species introductions
Biodiversity
Conservation Biology
Goal directed science that aims at understanding and
countering the loss of biodiversity
Hotspots: top preservation priorities
Ecological Restoration
Work designed to restore an ecosystem
that has been damaged or destroyed
Feeling bad? Do your part
Reduce energy consumption
Recycle and reuse
Help in restoration projects in your area:
Resource conservation district/ Restoration
ecology at UCR/ Environmental programs
division in Riverside County
THE END