Questions and Answers
What is the characteristic that unites protists as a group?
Which of the following is NOT a characteristic of protist cell surfaces?
What is a key difference between eukaryotic cells and prokaryotes?
According to the endosymbiotic theory, what is the origin of chloroplasts?
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What is the primary function of pseudopodia in protists?
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What is the term for protists that can obtain energy through both photosynthesis and ingestion of food particles?
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What is evidence for the endosymbiotic theory?
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What is a characteristic of mitochondrial and chloroplast DNA?
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What is the advantage of meiosis in protist sexual reproduction?
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What is a key difference between prokaryotic and eukaryotic cell division?
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Study Notes
Eukaryotic Origins
- Eukaryotic cells differ from prokaryotes in having a cytoskeleton and compartmentalization (nucleus and organelles).
- Eukaryotes appeared in microfossils about 1.5 billion years ago.
Evolution of Nucleus and Organelles
- The nucleus and endoplasmic reticulum arose from infoldings of the prokaryotic cell membrane.
- Many organelles evolved via endosymbiosis between an ancestral eukaryote and a bacterial cell.
Endosymbiosis
- Mitochondria evolved from aerobic bacteria engulfed by larger bacteria.
- Chloroplasts evolved from photosynthetic bacteria engulfed by larger bacteria.
- Chloroplasts originated from a single line of cyanobacteria.
- Hosts are not monophyletic, and brown algae engulfed red algae that already had chloroplasts, resulting in secondary endosymbiosis.
Evidence for Endosymbiosis
- DNA inside mitochondria and chloroplasts is similar to bacterial DNA in size and character.
- Ribosomes inside mitochondria are similar to bacterial ribosomes.
- Chloroplasts and mitochondria replicate by binary fission, not mitosis.
- Mitosis evolved in eukaryotes.
Mitosis
- Prokaryotes carry genes on a single DNA molecule, while eukaryotes have multiple chromosomes.
- Mitosis and cytokinesis developed to separate chromosomes and other cell contents during cell division.
- Mitosis evolved over thousands of years.
Overview of Protists
- Protists are the most diverse of the four eukaryotic kingdoms.
- They are united by not being fungi, plants, or animals, but vary considerably in other aspects.
- Protists can be unicellular, colonial, or multicellular, and have all types of nutrition and symmetries.
Classification of Protists
- Protists are not monophyletic, but are present in all six eukaryotic supergroups: Excavata, Chromalveolata, Archaeplastida, Rhizaria, Amoebozoa, and Ophisthokonta.
Cell Surface in Protists
- Protists have a varied array of cell surfaces, including plasma membrane, extracellular matrix (ECM), and diatoms with silica shells.
- Cysts are dormant cells with resistant outer coverings used for disease transmission.
Locomotion in Protists
- There are three primary means of locomotion: flagella, cilia, and pseudopodia ("false feet").
Nutrition in Protists
- Autotrophs can be photosynthetic or chemoautotrophic.
- Heterotrophs include phagotrophs that ingest particulate food matter, and mixotrophs that are both phototrophic and heterotrophic.
Reproduction in Protists
- Asexual reproduction is typical, and includes mitosis, budding, and schizogony.
- Sexual reproduction involves meiosis, producing haploid gametes that unite to form a zygote, allowing for genetic recombination.
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Description
This quiz covers the characteristics of eukaryotic cells, their origins, and the development of cellular structures such as the nucleus and endoplasmic reticulum.
