Eukaryotes ………let’s get organized

Protists and Multicellular Both the protists and all multicellular organisms are made up of Eukaryotic cells. Most multicellular organisms form symbiotic relationships with prokaryotes The adult human body is composed of tens of trillions of eukaryotic cells, but house hundreds of trillions of bacterial cells.

Characteristics of Eukaryotes Membrane bound organelles Defined nucleus housing the DNA Larger than prokaryotes DNA is organized into chromosomes, long strands of DNA usually tightly wrapped around protein molecules. The DNA is in doubled coiled linear strands, not looped into plasmids like in prokaryotes.

The Organelles Just as your body contains several specialized organs to carry out needed functions, each Eukaryotic cell has membrane bound organelles which carry out specific functions in the cell You will need to memorized each organelle, it’s function and be able to label it

Organelles In all cells: – Nucleus – ribosomes – Mitochondria – Lysosome – Golgi apparatus – Vacuoles – Plasma membrane – Cytoskeleton – Endoplasmic Reticulum In autotrophs (plant cells and algae) – Cholroplasts – Cell wall (in plant cells the vacuoles are usually larger and are used to hold and alter the shape of the cell using “tugor pressure)

Cellular Power The choloroplasts in photosynthetic cells produce sugars from light, while the mitochondria in all cells respires these sugars to release energy from them. The DNA in the nucleus of Eukaryotic cells do not code for the building of cholorplasts or mitochondrion, instead they house their own DNA and replicate on their own within the cell.

Interesting Power Houses The DNA in the cholorplasts and mitochondrion are not linear, but looped, and are not in a nucleus, but free within the structure. They contain only membranes and ribosomes (few organelles) to perform their activities – Does this sound familiar?

Single celled eukaryotes (Protists) Autotrophs use energy (usually sunlight) to make sugar from a carbon source (usually CO2) and water. Eukaryotic autotrophs are called algae As they are photosynthetic their names often end with the suffix “phyta” Algae along with phytoplankton (bacteria) produce about 70-80% of the Earth’s Oxygen and are the primary food source for most aquatic life.

Types of Algae Many algae are single celled Some interesting single celled algae include: – Euglena’s / Euglenophyta (the missing link?) Euglena’s have photosynthetic chloroplasts like plants or plant-like protists. But they lack a rigid cell wall, have a photosensitive spot, a flagellum for motion, and they ingest food particles in the dark like animals, or animal- like protists. Euglena’s are small, and when conditions are unfavorable (too hot) they grow a thick wall (cyst) around themselves and go dormant (like many bacteria)

More algae Diatoms are unique because they have cell walls made not of carbon based starches or cellulose fibers, but of silicon based crystal filaments (like glass). When they die there cell walls rarely decompose and thus form diatomaceous earth, packed forms include limestone. The inner organic material decomposes anaerobically and forms most of the earth’s fossil fuels. (not dinosaurs)

Multicellular algae Algae can grow in colonies where the cells group together. These form slime (slime molds) and multicellular algae often miss-named seaweed These include: Chlorophyta (green algae) Phaeophyta (brown algae), Rhodophyta (red algae) and Chrysophyta (golden brown algea, cell walls made of a mixture of cellulose and silicate fibers)

The start of specialization These algae grow in colonies, as do some forms of bacteria, but these bacteria begin to show specialization. Some of them group into long filaments called “holdfasts” which secure the base of the colony to the ground or rocks underwater. Another group form the stem- like structure called a stipe, and still others form the “blade” of the algae which collects most of the light and does the bulk of the photosynthesizing, like leaves.

Multicellular Algae

Algae - Plants It is believed that some algae growing in tidal regions where sometimes exposed developed into modern plants.

Blue-green Algae…….not! The species often referred to as blue-green algae are not really algae, but colonies of cyanobacteria (a type of bacteria that contains chlorophyll)

Protozoans…….animal like protists “zo” like “zoo” referring to animals Protozoans do not have rigid cellulose cell walls, or contain chloroplasts. The take in food particles, sometimes bacteria or smaller protists. They often move by means of whip like flagella, or many short hair like cilia Some like amoebas move by pushing out a small portion of itself called a pseudopod, then filling itself into the pseudopod

Common protozoans Flagellates; move by flagella, usually 2 or more – Euglenozoa……..yep remember euglena’s have characteristics of both plant and animal like protists. Some varieties even do not contain chloroplasts, so some books refere to them as euglenozoas. – dinoflagellates

cilliates;…..move by cillia – Paramecium Ameobazoa….move by changing shape (pseudopods) – Ameoba’s

Protists movement C7k C7k

Assignment Try #1-10, end of chapter review page 398, (chapter 17)