Transcript Ecology - One Day Enrichment

Ecology
Chapters 3-5
Biology – Miller • Levine
What is Ecology?
• The scientific study of:
– Interactions among organisms
– Interactions between organisms and their
environment
• Biosphere – portions of the Earth where
life exists (land, water, and air)
Levels of Organization
• Species – group of organisms that can breed
and produce fertile offspring
• Population – a group of individuals of the same
species that live in the same area
• Community – different populations that live in
the same area
• Ecosystem – all the organisms plus the
nonliving environment
• Biome – group of ecosystems with the same
climate and similar communities
Levels of Organization
Energy Flow
• Sunlight is the main energy source for life
on Earth.
• Autotrophs (producers) – organisms that
make their own food
– Photosynthesis – use light energy to make
food
– Chemosynthesis – use chemical energy to
make food
Energy Flow
• Heterotrophs (consumers) – organisms
that must feed on other organisms for
energy
– Herbivores – eat only plants
– Carnivores – eat other animals
– Omnivores – eat both plants and animals
– Detrivores – feed on dead matter
– Decomposers – break down organic matter
Feeding Relationships
• Energy flows through an ecosystem in one
direction (sun → producers → consumers)
• Food chain – a series of steps in which
organisms transfer energy by eating and being
eaten
Feeding Relationships
• Food web – a network
of complex feeding
interactions
• Trophic levels – each
step in a food chain or
food web
– 1st – producers
– 2nd – primary consumers
– 3rd – secondary
consumers
– 4th – tertiary consumers
Ecological Pyramids
• Energy Pyramid – shows the amount of
energy available at each trophic level
– Only about 10% of the energy is transferred to
the next level
• Biomass Pyramid – shows the amount of
living tissue within each trophic level
• Pyramid of numbers – shows the number
of organisms at each trophic level
Ecological Pyramids
Biotic and Abiotic Factors
• Biotic factors – the living things that
influence organisms
• Abiotic factors – the nonliving things that
influence organisms
– Light
– Soil
– Wind
– Water
– Temperature
Habitat and Niche
• Habitat – the area
where an organism
lives
• Niche – the role an
organism plays in its
habitat
– No two species can
share the same niche
in the same habitat
Community Interactions
• Symbiosis – any relationship in which two
species live closely together
– Mutualism – both species benefit (flowers &
insects)
– Commensalism – one species benefits while
the other is neither helped nor harmed
(orchids in a rainforest)
– Parasitism – one organism benefits while the
other is harmed (fleas on a dog)
Symbiosis
Ecological Succession
• The series of changes that occurs in a
community over time
• Primary succession – occurs on surfaces
where no soil exists (no previous life)
– Pioneer species – the first species to
populate the area
– Lichens → mosses → grasses → shrubs →
trees
Primary Succession
Ecological Succession
• Secondary Succession – when a
disturbance changes the existing
community without removing the soil
– Tornadoes, fire, clear cutting
– Occurs much quicker than primary succession
– Climax community – the relatively stable
final community
Populations
• Population density – the number of
individuals per unit area
• Population growth – increase in size of a
population
• Population size can be affected by:
– Number of births
– Number of deaths
– Immigration – organisms moving into an area
– Emigration – organisms moving out of an area
Exponential Growth
• Under ideal conditions
with unlimited
resources, a
population will grow
exponentially
• J-shaped curve
Logistic Growth
• As resources
become less
available, the
growth of a
population slows or
stops
• S-shaped curve
Limiting Factors
• A factor that causes population growth to
decrease
• The population size will usually remain
constant
• Creates the s-shaped curve
• Two kinds of limiting factors:
– Density-dependent
– Density-independent
Density-Dependent Factors
• A limiting factor that depends on
population size
• Competition – organisms compete for
resources
– Between members of the same species
– Between members of different species
• Parasitism and disease
Density-Dependent Factors
• Predation – when one species feeds on
another
– Predator – the organism that feeds on the prey
– Prey – the organism being eaten
Density-Independent Factors
• Affects all populations, regardless of the
population size
• Unusual weather – heavy storms
• Natural disasters – tornado, volcanic
eruption
• Seasonal cycles – insects die during winter
• Human activities – clear-cutting forests
Human Population Growth
• At first the human population grew slowly
• About 500 years ago it started increasing
rapidly
• Resembles the J-shaped curve
US & World
Populations