Overview
This lecture provides an overview of the key features and differences among animals, plants, fungi, protists, bacteria, and viruses, focusing on their classification and unique characteristics.
The Five Kingdoms of Life (Excluding Viruses)
- Animals, plants, fungi, protists, and bacteria make up the five kingdoms of life.
- Viruses are not classified as living organisms and are excluded from the kingdoms of life.
Eukaryotes vs. Prokaryotes
- Animals, plants, fungi, and protists are eukaryotic, meaning they have cells with a nucleus and DNA in chromosomes.
- Bacteria are prokaryotic, lacking a nucleus and with DNA free-floating in the cell.
- Eukaryotic cells are 10-100 times larger than prokaryotic cells.
- Viruses are much smaller than both eukaryotic and prokaryotic cells and lack cellular structure.
Animals
- Animals are multicellular organisms (many cells per organism).
- They are heterotrophs, requiring energy from consuming other organisms.
- Most reproduce sexually and there are 5-10 million species.
Plants
- Plants are multicellular organisms.
- They are autotrophs, obtaining energy through photosynthesis using sunlight.
- Estimated 300,000 species exist.
Fungi
- Fungi can be multicellular (e.g., mushrooms) or unicellular (e.g., yeast).
- They are heterotrophs, but primarily saprotrophs, feeding by digesting food outside their bodies using enzymes.
- Multicellular fungi have a mycelium made up of hyphae.
- Some fungi are pathogens, causing diseases like athlete's foot.
Protists (Protctists)
- Protists are mostly unicellular but very diverse.
- Some resemble plant cells (photosynthetic), others resemble animal cells (consume other organisms).
- Some protists can be pathogens, such as Plasmodium (causes malaria).
Bacteria
- Bacteria are single-celled prokaryotic organisms found everywhere.
- Some photosynthesize, but none have chloroplasts.
- Most feed on living or dead organic matter.
- Estimated to have more species than all other kingdoms combined.
- Most are harmless or beneficial, but some are pathogenic (e.g., Salmonella).
Viruses
- Viruses are non-living particles, not made of cells and much smaller than bacteria.
- Composed of a protein coat and genetic material (DNA or RNA).
- Can only reproduce by infecting living cells; are considered obligate parasites.
- All viruses are pathogens, causing diseases in other organisms.
- Examples include influenza virus, tobacco mosaic virus, HIV, and COVID-19.
Key Terms & Definitions
- Eukaryote — organism with cells containing a nucleus.
- Prokaryote — organism whose cells lack a nucleus.
- Multicellular — organism made of many cells.
- Unicellular — organism made of a single cell.
- Autotroph — organism that makes its own food via photosynthesis.
- Heterotroph — organism that obtains energy by consuming others.
- Saprotroph — organism that digests food externally and absorbs nutrients.
- Mycelium — mass of hyphae forming the body of multicellular fungi.
- Parasite — organism that lives off another organism, often causing harm.
- Pathogen — organism or particle that causes disease.
Action Items / Next Steps
- Review the differences among the five kingdoms and viruses.
- Familiarize yourself with key terms and definitions for future lessons.