Cellular Diversity

Life Science: Molecular

Diversity of Cellular Life Unicellular Organism

Bacteria Archaea Multicellular OrganismCell SpecializationLevels of Organization –cells –tissues –organs –organ systems

Cells are the basic unit of structure and function in living things.

Three Domains There two categories of cells prokaryotes and

eukaryotes. The domains are the three major divisions of life, Bacteria, Archaea, and Eukarya.

Prokaryotes Eukaryotes

Bacteria Archaea Eukarya

Three Domains

5

ProkaryotesA unicellular organism is an organism that is made up of only one cell. All prokaryotes are unicellular organisms.

Leptospira (bacteria) E. coli (bacteria)

ProkaryotesBacteria are single-celled prokaryotes. Archaea are prokaryotes that thrive in extremely harsh conditions (extremophiles).

Bacterial Cell Bacteria and archaea are prokaryotes. They are

simple cells, with no internal organization.

BacteriaWe can’t live without bacteria. Our bodies have millions of bacteria on our skin and in our nose, mouth, and gut. Bacteria help us digest our food, make vitamins, and fight off harmful bacteria.

Eukaryotes are organisms with a nucleus and specialized structures called organelles.

Eukaryotes

Volvox (algae)

Yeast (fungi)

Unicellular Multicellular

Animal Cell Animal cells are eukaryotes. Animal cells also

contain centrioles and lysosomes.

Plant Cell Plant cells are eukaryotes. Plant cells also contain

chloroplasts and a cell wall.

Origin of Eukaryotic Cells• The endosymbiotic theory states that about 2

million years ago eukaryotic cells formed from a symbiosis with several different prokaryotes.

Aerobic bacteria

Ancient Prokaryotes

Ancient Anaerobic Prokaryote

Primitive Aerobic Eukaryote

Primitive Photosynthetic Eukaryote

Chloroplast

Photosynthetic bacteria

Nuclear envelope evolving Mitochondrion

Plants and plantlike protists

Animals, fungi, and non-plantlike protists

Multicellular Organisms• Multicellular organisms contain many different

kinds of cells that work together. • In multicellular organisms cells are specialized for

the type of work they do.

Levels of Organization• The levels of organization in a multicellular

organism are:

Cells

Tissues

Organs

Organ Systems

Cells• Specialized cells perform particular tasks in an

organism. Work is divided up among the different types of cells.

Tissues• A tissue is a group of similar cells that perform a

particular function.

Four Main Tissue Types: Epithelial TissueConnective TissueMuscle TissueNerve Tissue

Organs • An organ is many groups of tissues working

together to perform a function.

Organ Systems• An organ system is a group of organs that work

together to perform a specific function. • There are 11 major organ systems in the human

body, including the muscular, skeletal, circulatory, and nervous systems.