3. 1.3 How Are Living Things Different?
• Biodiversity: scope of variation among living
organisms
• Organisms can be grouped on the basis of whether
they have a nucleus (a sac that encloses and protects
a cell’s DNA)
• Prokaryote: single-celled organism without a nucleus (now
used only informally)
• Eukaryote: organism whose cells characteristically have a
nucleus
4. How Are Living Things Different? (cont’d.)
• Bacteria: most diverse and well-known group of
single-celled organisms that lack a nucleus
• Archaea: group of single-celled organisms that lack a
nucleus but are more closely related to eukaryotes
than to bacteria
5. How Are Living Things Different? (cont’d.)
A Prokaryotes are single-celled, and have no nucleus.
As a group, they are the most diverse organisms.
6. How Are Living Things Different? (cont’d.)
• Protist: diverse group of simple eukaryotes
• Fungus: single-celled or multicelled eukaryotic
consumer
• Breaks down material outside itself, then absorbs nutrients
released from the breakdown
7. How Are Living Things Different? (cont’d.)
B Eukaryotes consist of cells that have a nucleus. Eukaryotic
cells are typically larger and more complex than prokaryotes.
8. How Are Living Things Different? (cont’d.)
• Plant: multicelled, typically photosynthetic producer
• Animal: multicelled consumer that develops through
a series of stages and moves about during part or all
of its life
Figure 1.4 A few representatives of life’s diversity: A some prokaryotes; B some eukaryotes.
bacteria are the most numerous organisms on Earth. Top, this bacterium has a row of iron crystals that functions like a tiny compass; bottom, a resident of human intestines.
archaea resemble bacteria, but they are more closely related to eukaryotes. Top: two types from a hydrothermal vent on the seafloor. Bottom, a type that grows in sulfur hot springs.
Figure 1.4 A few representatives of life’s diversity: A some prokaryotes; B some eukaryotes.
protists are a group of extremely diverse eukaryotes that range from microscopic single cells (top) to giant multicelled seaweeds (bottom).
fungi are eukaryotic consumers that secrete substances to break down food outside their body. Most are multicelled (top), but some are single-celled (bottom).
Figure 1.4 A few representatives of life’s diversity: A some prokaryotes; B some eukaryotes.
plants are multicelled eukaryotes. Most are photosynthetic, and have roots, stems, and leaves.
animals are multicelled eukaryotes that ingest tissues or juices of other organisms. All actively move about during at least part of their life.
