Diversity of livinng Diversity of livinng OrganismsOrganisms

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Department of biology

Cell Structure is Evidence Cell Structure is Evidence for Relatednessfor Relatedness

• There are two main types of cells, prokaryotes and eukaryotes.

• Prokaryotes are bacteria. (Monera) Prokaryotes are much simpler and usually much

smaller than Eukaryotes.

• Eukaryotes are represented by the remaining four kingdoms: Animalia, Plantae, Fungi, and Protista.

• Monera (Prokaryota) :

http://community.webshots.com/photo/95521344/95541019zbQjjB

http://fig.cox.miami.edu/Faculty/Dana/monera.html

• Prokaryotes are simple cells. • The DNA is loose in the cytoplasm—there is no separate

nucleus. • The ribosomes are also in the cytoplasm.• In prokaryotes, transcription (synthesis of RNA) and

translation (synthesis of proteins) occurs simultaneously.• The cell is surrounded by a membrane, but there are no

internal membranes.• Outside the membrane is a cell wall, and sometimes an

outer capsule which can have structures projecting form it.

• Bacteria move using flagella: whip-like hairs similar to the flagellum of a sperm cell.

Bacterial ReproductionBacterial Reproduction

• Bacteria reproduce by the process of binary fission. The circular chromosome replicates its DNA. Then, the cell splits into 2 halves, each containing a single chromosome

• No spindle apparatus (as exists in eukaryotic mitosis and meiosis).

Shape: coccus (spheres) and bacillus (rods). Spirillum (spiral) is less common.Aggregation of cells: single cells, pairs (diplo), chains (strepto), clusters (staphylo).Thus we have types such as diplococcus (pair of spheres) and streptobacillus (chain of rods).

Exercise one Exercise one

Eukaryotic cell componentsEukaryotic cell components

• Cell wall (optional)• Plasma membrane• Cytosol containing organelles:

* Nucleus – DNA in chromosomes* Other membrane-bound organelles

• Mitochondria• Chloroplasts (optional)

* Ribosomes* Membrane system

• Flagella (optional)

Eukaryotic vs. prokaryotic cellsEukaryotic vs. prokaryotic cells

• Size* Prokaryotes ≤ 10 µm* Eukaryotes ≥ 10 µm

• Complexity* Prokaryotes – simple* Eukaryotes – complex

• Location of chromosomes* Prokaryotes – free in cytosol* Eukaryotes – within a nucleus

• Flagellar mechanisms differ

Bacteria & Archea

protists, Fungi, Plants, Animals

Bacterium (prokaryote)

Animal (eukaryote)

Plant (eukaryote)

Figures 7.4, 7.7, 7.8

(Actual size relative to eukaryotes below)

• Protista – single celled with a nucleus

http://www.mcwdn.org/Animals/Paramecium.html

• Euglena sp.* Members of the Euglenid group of the clade

Euglenozoa* Characterized by an anterior pocket from which one

or two flagella emerge, and the storage polysaccharide paramylon

- The eyespot functions as a light shield allowing only certain light rays to strike the light detector- The pellicle is constructed of protein bands beneath the plasma membrane and provides strength and flexibility

..NutritionEuglena are mixotrophic –Perform photosynthesis in the lightLose chlorophyll in the dark & absorb organic molecules via the plasma membraneLocomotionLocomotion is either swimming (flagellar motion), gliding, or euglenoid movement1

Euglena exhibit positive phototaxis – the light detector senses light, the flagellum propels the Euglena toward itOsmoregulationEuglena are hypertonic to their freshwater environmentWater enters by osmosis and needs to be removedThe contractile vacuole fills with water and then fuses with the gullet to release it

II. ProtistaII. ProtistaA. General Info

B. Groups1. Protozoa (“Animal-like”)- heterotrophs

Amoeba use “pseudopodia” to move

Paramecium-uses cilia to move

Macronucleusw/ micronuclei

behind

Oral groove on surface

Site of cell “anus”

Food vacuoles

Cilia

Undulating membrane in groove (ciliary)

Contractile vacuoles

Food particles

Paramecium, a ciliated protozoan