Transcript Human Ecology Lecture 1

Human Ecology
Lecture 1
Ecosystems
What is an Ecosystem?
An ecosystem has both biotic
(living) and abiotic (non-living)
components.
A community is made up of:
populations of organisms interacting
and inhabiting the same area at the
same time. Ecosystem is a
community plus it’s physical
environment
Ecological Niches:
roles filled by each member in an
ecosystem.
Producers:
organisms that carry out photosynthesis.
Consumers:
heterotrophs that consume food already
formed.
primary consumers :
herbivores, plant-eating organisms
Secondary consumers:
carnivores which eat primary consumers.
Omnivores:
organisms that eat both plants and animals.
Decomposers:
organisms which consume dead or
decaying matter.
Movement of energy in an
ecosystem
Energy cannot be created or destroyed, it is lost
as heat when energy is transformed from one
form to another form.
food chains and Food webs show who eats
whom
Grazing food chain- producer > primary
consumer > etc. In a community.
Detritus food chain - this is based on
decomposers
Decreasing energy available at each
trophic level; 90% of the energy
consumed at each level is lost as heat
leaving only 10% of it to be incorporated
by the next trophic level.
Energy from sunlight provides energy
needed in an ecosystem.
Producers capture energy
Energy flows in one direction
food webs-
all the interconnecting food chains in an
ecosystem
Ecosystems continue because they cycle
nutrients, use resources, and keep their
populations stable.
Cycles in the Ecosystem
Nutrients cycle through
communities.
Water cycle
Carbon cycle
Phosphorus cycle
Nitrogen cycle
Succession
The sequential change in a dominant species
in an area until a climax community is reached.
Primary Succession
Occurs when there has never been soil and
lichens and mosses contribute to soil
formation.
Secondary succession
Occurs in areas with soil, such as,
abandoned agricultural fields, it begins
with herbaceous plants >shrubs>trees>until
the climax community is reached.
As succession proceeds, the variety of
species increases, the community
becomes more able to recycle nutrients
and use energy efficiently
Climax communities have
difficulty recovering from
disturbance. The more diverse
the community, the more fragile
and sensitive it becomes.
Humans harm ecosystems by:
Destruction of habitat- agricultural practice
Pollution
Over hunting
Introducing alien species
Changes in the ecosystem
Population fluctuations caused by:
Limiting factors: competition, predation
etc.
Disturbances in the food chain- over
hunting, pesticide use, biomagnification.
Humans impact on Ecosystems
Mature natural ecosystems are stable
over time. Human activities alter these
ecosystems.
Pollution
Fertilizers
Pesticides
Herbicides
Over irrigating
Excessive fuel consumption
Problems with cities
Dependence on farms for food resources
Taking up more land Challenges of cities
for housing
Not conserving and reusing resources
generation of huge amounts of pollution
Population increases
Biological Magnification (Biomagnification)
Ecological Relationships
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Predation – Predator/ Prey +/Parasitism – Parasite/ Host +/Mutualism – benefits both +/+
Commensalism - one benefits other
unaffected +/0
• Competition -/-