Transcript CH4SC - St. Olaf Pages

CH4
A couple things in this chapter we already covered
We will talk about biomes and evolution on
Thursday!
The Six Kingdoms
Figure 20.20
Euglenozoans
Forams
Diatoms
Red algae
Green algae
Land plants
Domain Eukarya
Ciliates
Amoebas
Fungi
Animals
Methanogens
COMMON
ANCESTOR
OF ALL LIFE
Thermophiles
Domain
Archaea
Nanoarchaeotes
Proteobacteria
Chlamydias
Spirochetes
Gram-positive
bacteria
Cyanobacteria
(Chloroplasts)*
Domain Bacteria
(Mitochondria)*
Ecology is the study of
• the interactions between species and their
physical (abiotic) environment (Examples?)
• the interactions between and within species
(Examples?)
What do these things mean?
We will focus on the second one….between and
within species.
Many ecologists like to categorize the different
kinds of interactions between organisms by their
effect on both members of the interacting pair…
Is the interaction positive in terms of survival and
reproduction or negative?
What kind of an interaction might be bad for both
members of the interaction (have a negative affect
on survival and reproduction)?
Competition
We need to distinguish whether competition is …
Intraspecific
Interspecific
And whether it is ….
Interference..
when actually interact
Exploitation..
use common resources that are in short supply-”get
there first”
Do plants and phytoplankton compete? How?
What is an example of an interaction where one
member of the pair gains in terms of survival and
reproduction and the other loses?
Predation
An organisms that feeds on another organism.
If a parasite feeds on an organism but does not kill it
should we still call it a predator?
What is an example of an interaction where both
members of the pair gain in terms of survival and
reproduction? Example?
Mutualism!
What is it called when one gains while the other
neither benefits or gains? Example?
Commensalism!
Or to both individuals if INTRASPECIFIC!
Where would herbivory fit in?
Problems….
•Predators do not always eat other animals- we
consider squirrels seed predators (eat whole individual
seed-baby plant)
•Not all predators are animals- plant predators (venus
flytrap), protists (amoeba)
•Some herbivores kill the plant they feed on!
•In some ways herbivores are a little like parasites
(consume part of organism but do not kill) just don’t
happen to live on…
•Some parasites kill their host so should they be
predators?
•So in reality a continuum of “bewildering” interactions...
Which of these kinds of interactions do you think are
the most common? The most “important”?
Which of these most affects the flow of energy and
chemicals through the food web?
Are negative interactions (competition, predation) or
positive interactions (mutualism) more important?
If you mostly spent your days watching animal
planet, discover channel or youtube video clips
which would you think was most important?
A closer look at mutualisms!
(some positive interactions)
Tight and coevolved mutualisms
• leaf cutter ants and their fungus they farm
Loose, facultative mutualisms
• plants that have seed dispersal by vertebrates
•plants that nurse other plants by making suitable
conditions underneath them
•you and your surface bacteria
•kelp that provides home for inverts/fish
How tell the difference between these?
Ask… Would partners persist in absence of one
another? Are there specific evolved traits?
Lets go over some tightly coevolved mutualisms…
1. Mycorrhizae (fungi) and plants
•Surround roots or penetrate root cells
•Most all plants have (90%)
•First plants to live on land seemed to have had this
relationship
•Plants get water, minerals/ fungi gets sugars
2. Lichen
Algae shares
photosynthetic
materials, fungi
contributes minerals
+ place to live
3. Corals house different algal species
• algae receive nutrients (nitrogen+phosphorous) from
their coral animal partner
•coral receives organic compounds synthesized by
algae during photosynthesis
•corals can feed on zooplankton in night and get
photosynthetic products by day!
“Nature” of relationship unclear….
•corals induce the algal cells to release organic
compounds
•corals also seem to control rate of population growth
•These algae can live on their own in the water and
are happy there……Is this farming?
4. Legumes and bacteria
Bacteria fix nitrogen and obtain photosynthetic
products supplied by the plants.
Each legume is associated with a different bacterial
species.
Swellings are called nodules.
“Nature” of relationship is unclear here too….
•Bacteria are common in soil (bacteria not dependent)
•Plant may
control
reproduction of
colony by
releasing a
specific chem
•Farming?
5. Cellulose digesting mutualists
gut bacteria and protists play critical role in digestion of
plant material
Ruminants have 4 chambered stomachs-basically big
fermentation chambers (Microorganisms make up about
a quarter of volume)
Termites and wood cockroaches are similar..have
protists that also have their own internal bacterial
community
Now what do you think? Is the world dominated by
negative or positive relationships?
Negative-predation, competition
Positive-mutualisms
Connects to a historical debate!
Frans Snijders (1579-1657)
Peter Paul Rubens, Tiger and Lion Hunt,
c. 1617–1618.
Alfred Lord Tennyson's In Memoriam A. H. H., 1850.
Who trusted God was love indeed
And love Creation's final law
Tho' Nature, red in tooth and claw
With ravine, shriek'd against his creed
Arthur Henry Hallam
Hereupon, the beasts, enraged at the humbug, fell
upon him tooth and claw.
They were highlighting “the apparent conflict between
love as the basis of the Christian religion and what
they saw as the callousness of nature.”
http://www.phrases.org.uk/meanings/red-in-tooth-and-claw.html
How do these interactions play out at the next level
up??
Communities
The “nature” of communities…p93 4.4
Historical and current Debates concerning Communities
Two views of Communities
Clements vs Gleason
• Clements believed communities are like
organisms or “superorganisms” with different
species or populations paralleling different
organs in a body
• Gleason believed they are “chance
assemblages” of species each of which is just
responding to certain physical requirements
(moisture levels, sunlight)
If communities are like superorganisms then what
might you expect the relationships between
organisms within a community to be..loose or tight?
What might happen in the community if a species
was lost to extinction?
If a prairie was one community and the forest
another what would the boundary between the two
look like?
Well defined or unidentifiable as you walked from
one to another?
Contrast with Gleason
If organisms are chance assemblages then ……
•casual interactions between species
•removing a single species may not have an effect
on community properties, structure
•communities intergrade continuously (no real
boundary between one community and another)
Gleason INDIVIDUALISTIC HYPOTHESIS
If communities are like superorganisms then there
will be
•strong, tight interactions between species
•removing a single species may have a big effect on
community properties, structure
•real boundaries when move from one community to
the next
Clement =INTERACTIVE HYPOTHESIS
Fig 53.1
Cambpell
Which of these graphs represents what you might find if
communties were the way Clements sees them?
Which one represents communities the way Gleason
sees them?