Overview
This lecture provides an overview of the key features and differences between animals, plants, fungi, protists, bacteria, and viruses, focusing on how to distinguish these major biological groups.
The Five Kingdoms of Life (Excluding Viruses)
- Animals, plants, fungi, protists, and bacteria make up the five kingdoms of life.
- Viruses are not considered living organisms and are not included in any kingdom.
Eukaryotes vs. Prokaryotes
- Animals, plants, fungi, and protists are eukaryotes, meaning their cells have a nucleus and DNA in chromosomes.
- Bacteria are prokaryotes; their DNA floats freely in the cell without a nucleus and they are smaller than eukaryotic cells.
- Viruses are neither prokaryotic nor eukaryotic and are even smaller than bacteria.
Animals
- Animals are multicellular organisms.
- They are heterotrophs; they obtain energy by consuming other organisms.
- Most animals reproduce sexually.
Plants
- Plants are multicellular and contain chloroplasts.
- They are autotrophs; they use photosynthesis to produce energy from sunlight.
Fungi
- Fungi can be multicellular (e.g., mushrooms) or unicellular (e.g., yeast).
- They do not photosynthesize and obtain energy by breaking down other organisms (heterotrophs or saprotrophs).
- Multicellular fungi have a mycelium made of hyphae.
- Some fungi can act as pathogens, causing diseases like athlete's foot.
Protists (Protctists)
- Nearly all protists are unicellular, but vary greatly.
- Some, like Euglena, photosynthesize; others, like amoeba, consume organisms for energy.
- A few protists are pathogens, such as Plasmodium (malaria).
Bacteria
- Bacteria are unicellular prokaryotes found everywhere, including on and in humans.
- Some bacteria photosynthesize, but none have chloroplasts.
- Most feed on living or dead organisms.
- Bacteria can be pathogens (e.g., Salmonella) or beneficial (e.g., gut bacteria).
Viruses
- Viruses are non-cellular particles much smaller than bacteria.
- They have a protein coat and genetic material (DNA or RNA).
- Viruses are parasites; they must infect living cells to reproduce.
- All viruses are pathogens and cause diseases in various organisms.
Key Terms & Definitions
- Eukaryote — organism with cells that have a nucleus (animals, plants, fungi, protists).
- Prokaryote — organism with cells lacking a nucleus (bacteria).
- Heterotroph — organism that obtains energy by consuming others.
- Autotroph — organism that produces its own energy, usually via photosynthesis.
- Saprotroph — organism that feeds by externally digesting dead material.
- Pathogen — organism or particle that causes disease.
- Mycelium — mass of hyphae forming the body of multicellular fungi.
- Virus — non-living particle that needs host cells to reproduce.
Action Items / Next Steps
- Review and memorize the main differences between the kingdoms and viruses.
- Prepare for questions comparing cellular features and ways of obtaining energy.