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B20 Ch3 Biomes, Ecosystems and Populations:
WHY AREN’T SPECIES DISTRIBUTED EVENLY ACROSS THE EARTH?
How do Biomes affect species distribution? Why are there specific biomes in specific
latitudes? Pg. 93-103
BIOME – An ecosystem or group of ecosystems in a specific region on Earth that has a
particular combination of biotic and abiotic factors; for eg, tundra, desert,
rainforest, taiga, etc. The unequal heating of Earth and differences in rainfall
creates different climates a different latitudes.
Temperature and Precipitation and their Effects on Biomes of the World
How do LIMITING FACTORS affect species distribution?
Limiting factors provide checks and balances on population numbers, population cycles, and
create unique habitats and ecosystems. Limiting factors are biotic and abiotic.
LIMITING FACTOR
• A limi ng factor is any bio c or abio c element that controls
the number of individuals in a popula on. Bio c limi ng
factors include compe on, preda on, and parasites.
Limiting factors prevent these
bacteria from reproducing
infinitely.
Limiting factors affect the productivity of ecosystems.
Productivity: the rate at which an
ecosystem’s producers capture
radiant energy and store it in
organic compounds ( J/m2/yr or g/
m2/yr). Productivity depends on
many variables, including # of
producers and how much heat,
light and moisture is available.
 Choose 3 of your favorite ecosystems in the graph above and list some limiting abiotic
and biotic factors found in each. Put this in a table. Explain the graph results for the 3
ecosystems.
Biotic Factors:
Competition, predators, parasitism pg. 101 – 103. How do these factors
provide checks and balances and cause regular population cycles?
https://www.youtube.com/watch?v=GxE1SSqbSn4&index=4&list=PL8dPuuaLjXtNdTKZkV
_GiIYXpV9w4WxbX Crash Course Community Ecology
https://www.youtube.com/watch?v=D1aRSeT-mQE&list=PL1584FDFF24D0F6A2
Competition, Predation and Symbiosis
 Brainstorm how species limit inter- and intra – specific competition – because if they
don’t then one species will outcompete the other and one will go extinct.
(Hint: Remember from the Crash Course Clip the Principle of Competitive Exclusion and
realized niche vs. fundamental niche)
1. COMPETITION: What’s different about these pairs in terms of competition?
 Generalists – ex.
vs
 Intraspecific competition– ex.
(within a species)
vs. interspecific competition – ex.
(between species)
specialists – ex.
MacArthur’s Famous Warble Study
2. PREDATORS AND PARASITES:
 What are the checks and balances in these interactions?
PREDATOR:PREY CYCLES
PARASITISM
ANIMAL PARASITES
The parasite lives and feeds off of a
host. It rarely kills the host, but
weakens it. The parasite is usually
smaller than the host.
One organism can have many
parasites.
3. Invasive Species: What happens when there aren’t checks and balances?
https://www.youtube.com/watch?v=spTWwqVP_2s The threat of invasive species
How do scientists study ecological interactions in ecosystems?
Populations: a group of individuals of
the same species living in a specific
area.
A species = organisms that breed and
produce fertile organisms.
Population ecologists study:
• population size and how it changes over time
• age distribution
• # of females and males, limiting factors on their population
• carrying capacity
• habitat, niche, range
• interactions with other populations and their environment.
• succession
• zones
Carrying capacity (the population size that can be
supported by of an ecosystem for any species) is affected
by many situations, including seasonal change.
Habitat: Where do you live? What’s your
address?
Niche: What is your role in the ecosystem?
What do you do? Do you eat meat?
Range: What part of the biosphere (geological
area) do you live in?
The variety of niches and habitats within an ecosystem is determined by the biotic and
abiotic factors mentioned above, and determines the species diversity of an ecosystem.
Complex ecosystems offer more habitats and niches and thus promote greater species
biodiversity which is important for the stability of the ecosystem and its ability to withstand
change (resiliency).
The monocultures human’s create (i.e CHS football field, monocultures in agriculture, lawns,
reclamation) decrease species biodiversity, and limit an ecosystem’s ability to withstand
change.
SUCCESSION
Species diversity changes over time
from pioneer species to the climax
community.
ECOSYSTEM ZONES
Stromatolites and Earth’s changing atmosphere pg. 55-56
Stromatolites are made of fossilized ancient bacteria – primarily photosynthetic
cyanobacteria that scientists believe caused the sudden increase in oxygen in the Earth’s
atmosphere billions of years ago changing it from an anaerobic to an aerobic environment,
greatly increasing species diversity.
Many stromatolites 2.5 billion years old or older have dark banding patterns caused by iron
in the ancient oceans combining with the O2 released by the photosynthesizing cyanobacteria and
forming black iron oxides.
Stromatolites less than 1.8
billion years old do not have
black bands, indicating that the
ocean’s iron ions were used up and
the O2 from the cyanobacteria was
now released into the atmosphere.
This changed the Earth’s atmosphere into an oxygen rich environment which over evolutionary
time evolved into the O2 dependent biosphere we have now.
https://www.youtube.com/watch?v=uU00tg98Jjw cyanobacteria explained!
Some primitive cyanobacteria entered a symbiotic relationship with early organisms –
these cyanobacteria became chloroplasts and opened up evolution for the huge variety of
photosynthetic organisms and the present day oxygen dependent ecosystem!
Taxonomy: How do scientists organize and classify all of this biodiversity?
At first there were 6 kingdoms, but with so many new species and increasing biochemical and
genetic information our taxonomic system is:
3 Domains – each subdivided into Kingdom, Phylum, Class, Order, Family, Genus, species.
(Mnemonic: Danish King Philip Came Over From Germany Sunday).
The Three Domains of Life
Bacteria: lack a membrane bound nucleus:
ex. bacteria that cause diseases and form
the microflora of our skin, nasal passages,
mouth, teeth, and gut
Archaea: lack a membrane bound nucleus, have a
distinctive cell membrane and cell wall
chemistry: ex. thermal vent bacteria
(chemosynthesis). Live in extreme
environments.
Eukarya: membrane bound nucleus: ex. humans!
Classification of living things: an introduction https://www.youtube.com/watch?v=vqxomJIBGcY
As you proceed within a domain from Kingdom down to
species, there are more similarities in the organisms in
each classification. Chordata share more characteristics
than Animalia. Homo sapiens (humans) share more
characteristics than a cat and a human even though they are
in the same Domain, Kingdom, Phylum, and Class.
Linnaeus devised a binomial naming system and named
every individual species by its unique Genus and species
name which we still use today.
Dichotomous keys have been devised to enable us to
identify living organisms to their genus and species name. Di
means two, chotomy means cut. In these keys there are
always 2 statements (“cuts”) and you observe the organism
you are trying to identify and you choose one of the 2
statements and proceed from there – check out pg. 89, and
#6 pg. 92.