Transcript Single-celled and colonial algae

Spring Break 2014!!
Biodiversity: Combination of the term biological
diversity, meaning the number and variety of organisms
in the world.
Biodiversity
Edward (E.O.) Wilson
(1929-)
Harvard professor,
author, ant biologist
Books: The Diversity of
Life (1992), Naturalist
(1994)
Biophilia: Humans’ tendency to love the natural world
Mindandocean.org
Wallace J. Nichols’ Blue
Mind movement
Why is biodiversity important?
Chinese red-headed centipede
Why is biodiversity important?
Venus’ flower basket
Why is biodiversity important?
In U.S., half of corn crop and ¾ of soybean and
cotton are genetically modified.
One tree of life, lots of twigs.
Phylogeny of all life
Microbe: Microscopic organism
History of Life on Earth
4.6 bya (billion years ago): Earth forms
4.0 bya: First life forms appear (prokaryotes)
2.7 bya: Photosynthetic prokaryotes start filling atmosphere with
oxygen
2.1 bya: First eukaryotes appear
1.2 bya: First multi-cellular eukaryotes appear
540 mya (million years ago): Cambrian explosion
500 mya: Movement onto land
Clicker Question
True/False: Cell respiration was a common process among
organisms 3 billion years ago.
a. False, because there wasn’t any glucose on the planet
b. True, because animals needed glucose
c. False, because there was very little oxygen in the
atmosphere
d. True, because there was enough carbon dioxide in the
atmosphere
Mass Extinctions
5 Mass Extinctions over the past 540 million years
Each time, more than half of species on Earth went extinct
End of Cretaceous (65 mya) marked end of dinosaurs
(although birds are dinosaurs)
Are we entering a sixth mass extinction?
Does size really matter?
Clicker Question
What does the author suggest may have directly caused the
Permian mass extinction?
a. Alien invasion
b. Increase in CO2 levels acidifying the oceans and increasing
temperatures
c. Increase in photosynthetic organisms
d. Decrease in CO2 levels leading to global cooling
Clicker Question
How does the author suggest the microbe Methanosarcina
affected Earth’s biodiversity?
a. These swamp-dwelling organisms released lots of CO2
which warmed the atmosphere
b. These sea-dwelling organisms released lots of methane
which warmed the atmosphere
c. These organisms were part of huge algal blooms that
occurred in the oceans and depleted them of oxygen
Estimate of number of species for different groups of organisms, from
Mora et al. (2011)
Prokaryotes
All single-celled
Have cell walls outside their
plasma membrane
No membrane-enclosed
organelles
Some harmful, but mostly
helpful
Prokaryotes are found everywhere, in all environments
3 Prokaryote Types
1. Spherical (Cocci)
2. Rod-Shaped (Bacilli)
3. Spiral
Cocci
Bacilli
Spiral
How do prokaryotes reproduce?
Asexual reproduction through binary fission: DNA duplicates,
then a single cell splits into 2, those 2 cells split into 4, then 8,
then 16…so on.
Remember, each cell is an entire organism, so prokaryote
colonies can grow very quickly!
Prokaryotes reproduce quickly, which is why we put our food
in the refrigerator!
Thought Question
Antibiotics are drugs we have developed to kill bacteria that
cause diseases. How might bacteria develop resistance to these
drugs very quickly?
Genetic recombination in prokaryotes
Prokaryotes don’t have sex, but they still occasionally share
genetic material through horizontal gene transfer.
Clicker Question
What is a source of genetic variation in prokaryotes?
a.
b.
c.
d.
e.
Mutation
Binary fission
Horizontal gene transfer
A and b
A and c
Archaea
Extremophiles: Lovers of the extreme; habitat is extreme
environments
Living on the edge
The pros and cons of bacteria
Harmful: Disease agents (pathogens), biological weapons
Beneficial: Symbiosis, nutrient recycling, bioremediation
Bacteria as pathogens
Exotoxins vs. endotoxins
(example: bacterial
meningitis)
What shape of bacteria are
these?
Biological Weapons
Anthrax
The friendlier side of bacteria
Bacteria are great environmentalists
Bioremediation
Bioremediation
The use of organisms to remove pollutants from water, air,
or soil.
Example: Sewage treatment, toxic chemical clean-up
Bioremediation
Thought Question
Given what you now know about prokaryotes, why is it so
hard to estimate how many species there are?
Goodbye prokaryotes, hello eukaryotes!
Can be single-celled or multi-celled (mostly singlecelled)
Have nucleus and other membrane-enclosed organelles
First appeared about 2.1 billion years ago
Protists
Protists in a drop of pond water
How did protists evolve?
Membrane
infolding; explains
origin of most
organelles.
Endosymbiotic origin of protists
Protist Diversity
Most are aquatic, some live in moist environments like
damp soil or leaf litter.
Different types of feeding:
Autotroph: Photosynthetic, such as algae
Heterotroph: Eat other organisms
Mixotroph: Photosynthetic and heterotrophic, depending
on conditions
Clicker Question
Which of the following is accurate about protists?
a. They evolved alongside prokaryotes and are mostly
unicellular
b. They are all photosynthetic and evolved from
prokaryotic ancestors
c. They have nuclei and reproduce by binary fission
d. They have nuclei and evolved from prokaryotic
ancestors
4 Types of Protist
1. Protozoans
2. Slime Molds
3. Single-celled and colonial algae
4. Multicellular, marine algae (seaweeds)
Protozoans
Mostly heterotrophs, live in aquatic environments, eat
other protozoans or absorb nutrients in water
Protozoans
4 Types of Protist
1. Protozoans
2. Slime Molds
3. Single-celled and colonial algae
4. Multicellular, marine algae (seaweeds)
Slime Molds
Plasmodial Slime Molds
Cellular Slime Molds
4 Types of Protist
1. Protozoans
2. Slime Molds
3. Single-celled and colonial algae
4. Multicellular, marine algae (seaweeds)
Single-celled and colonial algae
Algae in general: Photosynthetic protists that live in
marine and aquatic environments
Plankton: The community of microbes near the surface of
water environments dominated by single-celled algae
Diatoms (single-celled algae)
Colonial algae
4 Types of Protist
1. Protozoans
2. Slime Molds
3. Single-celled and colonial algae
4. Multicellular, marine algae (seaweeds)
Seaweeds
Not plants!
Large, multicellular, photosynthetic
Seaweeds
Seaweeds