1. Eukaryotic Evolution & Diversity
Sections 2.3 – 2.4

2. Introduction
3.5 billion years ago, prokaryotes were the only organisms on earth – surviving many harsh environments
However, for the past 2 billion years, they have co-existed with more evolved eukaryotic cells

3. Introduction Eukaryotic organisms are more complex than prokaryotes
They have more genes, which allows for more cellular diversity in size, shape, movement, and specialized functions
But …. How did they evolve exactly?

4. Endosymbiosis
One main theory is that eukaryotic cells resulted from the merger of 2 or more simpler cells
Endosymbiosis – one cell engulfs (swallows up) a different type of cell. The engulfed cell survives within the larger cell

5. Chloroplasts & Mitochondria
The theory of Endosymbiosis suggests that mitochondria and chloroplasts were once small, free-living prokaryotes and then were engulfed by larger cells – and survived inside these cells
Where:
The organelle (mitochondria / chloroplast) – is called an endosymbiont
The larger engulfing cell – is a host cell

6. Multicellularity
While this theory help give us some info on the evolution of eukaryotes
It DOES NOT account for all the Multicellularity seen in eukaryotes
So, scientists have hypothesized that the first multicellular organisms arose from colonies created by dividing individual cells
Genes within these cells now contained instructions for cells to become specialized in certain areas
For example – some cells specialized in absorbing nutrients (bacteria in soil), while others gathered energy from the sun (cyanobacteria)

7. Life Cycles and Reproduction
Reproduction of eukaryotic cells is much different (based on their more complex nature) than prokaryotes
Because of they exist within a wide range of organisms, they reproduce more complex and differently from one organisms to another

8. Life Cycles and Reproduction
For example, in humans eukaryotic cells undergo sexual reproduction – where gamete (sex) cells fertilize into a zygote and undergo further cell division
While in other smaller organelles they are able to reproduce asexually via multiple fusion and further cell division
Essentially, regardless of the form of reproduction, we see the sexual life cycles alternate between meiosis – producing haploid cells and fertilization – which produces diploid cells

9. Protists: Unicellular Eukaryotes
Section 2.4

10. Introduction
Protists – are large unicellular eukaryotes, that are diversely shaped and are NOT a fungus, plant, or animal

11. Animal-like Protists AKA – Protozanos = heterotrophs
Are animal-like because they consume other organisms for food (i.e. prokaryotes)
Some protozanos are Parasites, as they benefit from taking nutrients from other organisms around them
Are Categorized into 4 groups

12. Spore-forming Protists
Animal-like Protists
Amoeba-like Protists
Flagellates
Ciliates
Spore-forming Protists
They are found in fresh and salt water, in soil, and in animals
They have contractile vacuoles to get rid of excess water
They use flagella's (long hair extensions of their cell membrane) to move
Some of them live in water
Others are parasites that can cause disease.
They have hundreds of tiny hair-like structures known as cilia
Use the cilia to sweep food through the water toward them
Absorb nutrients from their hosts
Do not have cilia or flagella, so they cannot move on their own
Ex – Malaria

13. Fungus-like Protists
These protists absorb their food from dead organic matter
They are grouped into 2 groups, slime molds and water molds
Most fungus-like protists use psuepods, (“false feet”) to move around.

14. Fungus – like Protists Slime Moulds
Can be grouped into 2 sub-categories:
Plasmodial slime moulds – not see to the naked eye, which are often found on the ground of forests and fields. They feed by engulfing smaller particles into their cytoplasm
Cellular slime mounds – feed by ingesting small bacteria or yeast cells
Slime molds will continue to grow as long as food and water are available to it

15. Fungus – like Protists Water Moulds
Most of them are small single-celled organisms
Most live on dead organic matter = makes them decomposers
But others are parasites on fish, insects, and plants
Some parasitic water molds cause diseases
These protists still endanger crops today

16. Plant – like Protists
Contain pigments in their chloroplast that allow them to carry out photosynthesis
They are producers and consumers
They mostly use photosynthesis, but some eat other protists or absorb nutrients for food
They are known as algae

17. Plant – like Protists
Algae is multicellular and single celled, but the single celled type can’t be seen without a microscope
Single celled algae that floats near the surface of the ocean are phytoplankton.
Most multicellular algae are seaweed or kelp.

18. Plant – like Protists
Other types of plantlike protists are diatoms, dinoflagellates, and euglenoids
Diatoms
Dinoflagellates
Euglenoids
Single cellular
Live in salt and fresh water
Use photosynthesis
Their cell walls have silica and cellulose
Reproduce asexually via Mitosis
Most live in salt water
Have 2 flagella to help spin around
Sometimes are red and produce a strong poison which can get into the water and kill aquatic animals
Live mostly in fresh water
Have plant and animal characteristics
Move by using flagella to push them through the water

19. Review

20. Homework
Section 2.3 – pg. 71 # 1, 5, 6, 9, 11
Section 2.4 – pg. 78 # 1, 2, 8, 13