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PROTISTS - AMOEBA AND PARAMECIUM – September 16, 2015
Prokaryotes: a single-celled organism that lacks a membrane-bound nucleus.
-DNA is in cytoplasm
-Ex: bacteria
Eukaryotes: any organism whose cells contain a membrane-bound nucleus, which contains its DNA.
-Ex: Plants, Animals, Protists
Characteristics of Protists:
-All protists have a membrane-bound nucleus (“control center” within the cell).
-All protists contain other organelles (membrane-bound structures within a cell that perform specific jobs)
-Most live in wet places (oceans, lakes, swamps, damp soils.)
-Most are unicellular (made of one cell).
-Most have structures that help them move.
How do protists get energy?
-Autotrophs = get energy from the sun through photosynthesis.
-Heterotrophs = get energy by eating other organisms or by decomposing material.
-Mixotrophs = can get energy from the sun AND by eating other organisms (“mixing it up”).
AMOEBA
-Microscopic (small), unicellular (one cell)
protozoa (animal-like protist)
-Live in fresh water, salt water, in soil, and as
parasites in moist body parts of animals.
Structures of an Amoeba
-Plasma membrane: surrounds cell, allows
substances to pass in/out
-Nucleus: membrane-bound control center
-Food vacuole: digests food
-Cytoplasm: jelly-like substance within cell
-Contractile vacuole: pumps water out of cell
Amoeba Movement and Feeding
Pseudopodia: extensions of the cytoplasm that allows amoebas to move and
detect food; “false feet.” Also called cytoplasmic streaming.
Amoeba Reproduction
Amoebas reproduce by a type of asexual reproduction (1 parent) called binary
fission.
= DNA is replicated and cytoplasm pinches in half to produce 2 identical
daughter cells.
PARAMECIUM
Paramecium is a microscopic (very small), unicellular (one cell) protozoa (animal-like protist).
It is plentiful in freshwater ponds.
Structures of an Amoeba
Nucleus: “control center” of a cell.
Pellicle: thick membrane that give the paramecium its shape
Cytoplasm: jelly-like substance that holds all the organelles.
Cilia: hair-like projections that act like microscopic oars
Contractile vacuole: Remove excess water out of the cell; works like a
pump.
Oral groove: takes in food
Food vacuole: digests food
Anal pore: Removes waste
Paramecium Movement
-The outer surface of the cell is covered with many hundreds of tiny hair-like structures called cilia.
-Act like “microscopic oars”
-Can swim backwards, forwards, or rotate using the cilia.
-Moves so quickly that we have to add a thickening agent or quieting solution to the slide to slow it down to study it.
Paramecium Feeding
-The paramecium rotates on its axis as it moves through the water.
-Small particles of debris and food are collected and swept into the oral groove (6) and down the funnel-shaped gullet (7)
by the cilia that also helps it move.
-Eats small organisms such as bacteria, yeasts, algae and even other smaller protozoa.
Paramecium Reproduction
-Paramecium reproduce by conjugation and binary fission.
-Conjugation: 2 paramecia exchange nuclear material and then separate.
-Binary fission: cell replicates its DNA, cytoplasm pinches in half, and 2 new daughter cells are formed (cell then grows in
size and makes structures).
Paramecium Excretion
-Food waste left in a food vacuole is excreted through the anal pore (the vacuole and pore fuse.
-Other wastes left over from cellular activity (metabolic waste) simply diffuse through the pellicle.
-Excess water and some metabolic wastes are excreted through the contractile vacuole.