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Ecosystems and
Population Change
Interactions Within
Ecosystems
 Ecology – is the study of interactions
between organisms and their living and
non-living environments.
 SPCE –
 species
population
ecosystem
community
 Ecological Niche – an organisms role in an
ecosystem which includes its place in the food
web, habitat, breeding area, etc.
 Within ecosystems, each organism has its own
specific role or place. No two species fulfill
exactly the same role or ecological niche.
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If a new species (exotic species) is introduced into an ecosystem, competition will
result with any species that fulfills the same niche. Eventually, one of the two species
will be out -competed and cannot survive in the ecosystem. During this process, the
entire ecosystem will be disrupted.
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Example: European rabbits were introduced to Australia to provide sport for game
hunters. The rabbits had no natural predators, and became pests. The rabbit
infestation resulted in the destruction of plant matter, crops and land. Agricultural
grazing land became littered with rabbit holes that proved to be a hazard to grazing
animals. Rabbits also dug under fences, allowing dingo’s (a native Australian wild
dog) to sneak into paddocks and kill large numbers of sheep.
Population Terms for each
environment
 Biotic Potential: is the maximum
reproductive capacity of a population if
resources are unlimited
 Carrying Capacity: is the maximum
population size of the species that the
environment can sustain indefinitely,
given the food, habitat, water and other
necessities available in the environment
 Environmental resistance: Factors in
an environment such as predators,
competition, climate and food availability,
that keep its various populations from
reaching their maximum growth potential.
Limiting Factors
 Are environmental conditions that may
prevent populations from reaching their
biotic potential.
 Limiting factors may be biotic or abiotic
ABIOTIC FACTORS
 too much / little light
 temperature too cold
/ warm
 harmful chemicals in
the environment
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BIOTIC FACTORS
insufficient food
excessive predators
diseases or parasites
diminished ability to
compete
Terrestrial Ecosystems
 Terrestrial ecosystems are limited by four
major abiotic factors:
1. Soil: Provides nutrients for all plants
that grow on land. Poor quality soil is an
important limiting factor in many
ecosystems
2. Available Water:
Precipitation that collects above ground is called
surface water.
Ground water is found in the spaces between soil
and porous rock that percolates
(PERCOLATION)
The layer that is saturated with water is found
within the water table
3. Temperature: Many plants and animals
adapt to a specific range of seasonal
temperatures.
4. Sunlight: has an effect on all terrestrial
ecosystems. The amount of sunlight
usually varies with the geographical
location and with the canopy plants that
are growing in a specific area.
Sustaining Ecosystems
 Ecosystems are destined to change, gradually,
over time. Sadly, human induced changes
often leave ecosystems unable to replenish
resources and the delicate balance of life is
upset. Terrestrial and aquatic ecosystems
each have a unique set of limiting factors and
challenges that threaten their sustainability.
Our Field
Study
Kaeli’s powerpoint
Grassland Biome
Riparian Forest Biome
Biodiversity and Classification
 Scientists estimate that there are between 2 and
4.5 million different types of organisms on the
planet.
 Likely there are / were many more.
 To organize, name and group these organisms
based on similar characteristics, scientists use a
system called taxonomy.
 Taxonomy – the science of classification
according to presumed relationships
among organisms.
 Scientists use a hierarchical system,
where organisms are classified in a
series of smaller groups.
The 5 Kingdoms
 Prokaryotae – includes the bacteria (eubacteria
and archaebacteria (unicellular with no cell
nucleus)
 Protista – includes single celled plants and
animals and algae (unicellular with a nucleus)
 Fungi – includes the mushrooms, yeasts,
moulds (multicellular, decomposers)
 Plantae – includes the trees, flowers, mosses
and ferns (multicellular, photosynthesizers)
 Animalia – includes sponges, worms,
crustaceans, insects, and mammals
(multicellular and heterotrophic)
Hierarchical System
Most  Domain- Bacteria, Eukarya, Archea
General  Kingdom – Monera, Protista, Plantae,
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Most 
Specific
Fungi, Animalia
Phylum – sub-groups of each kingdom
Class
Order
Family
Genus
Species – organisms that are very similar
and can naturally interbreed to produce
fertile offspring
Binomial Nomenclature
 When organisms are assigned a scientific name,
the name is given in two parts, Genus species,
and the name is either written in italics or
underlined. This system is called binomial
nomenclature.
 Genus name indicates organisms that are
similar, and is always capitalized.
 Species name indicates organisms that are
different, and is written in lower case.
 Ex. Canis lupis
wolf
Canis domesticus
dog
 Naming some 2 – 5
million organisms
presents a challenge to
scientists. To overcome
this challenge,
dichotomous keys are
used to identify and
classify organisms based
on their characteristics.
 Scientists today believe
that organisms changed
over time.