List the characteristics shared by eukaryotes that distinguish them from bacteria and archaea.
Protists are a diverse group of organisms that includes all eukaryotes except the land plants, fungi, and animals.
With reference to synapomorphies, explain why protists are a paraphyletic group
[*] No synapomorphies define the protists. There is no trait that is found in protists but no other organisms.
live surrounded by water
Discuss how protists impact human health with a brief outline of malaria and red tides.
- Malaria - parasitic protist called Plasmodium. specialized for infecting host cell
- algal blooms occur when dinoflagellates, toxin-producing protists, reach high densities in an aquatic environment. impacts humans b/c concentration too much
Explain the ecological importance of protists in aquatic food chains and the global carbon cycle.
1/2 CO2 is fixed by primary producers via photosynthesis - carbon sink
Without protists, most food chains in freshwater and marine habitats would collapse
How did the advent of electron microscopy lead to major breakthroughs in understanding the diversity of protists?
expanded our understanding of how many of these little suckers there are
Through morphological and DNA sequence comparisons it appears that Eukarya can be divided into two broad monophyletic groups. Name these two groups and the key feature that distinguishes between them.
- the group Plantae includes the green plants
- the group Opisthokonta includes the fungi and animals.
What is direct sequencing and what has been discovered since it was directed at protists?
discovery of several new lineages of eukaryotes, tiny protists the size of bacteria.
What four features characterized early eukaryotic cells?
- single-celled organisms
- with a nucleus and endomembrane system,
- cytoskeleton, but no cell wall.
Contrast the structure and motion of the eukaryote flagellum with the prokaryote flagellum.
Discuss the evolution of the nuclear envelope.
The leading hypothesis for the origination of the nuclear envelope (and the endoplasmic reticulum) is that it is derived from the infoldings of the plasma membrane.
What are the proposed steps in the evolution of the mitochondrion?
endosymbiosis theory proposes that mitochondria originated when a bacterial cell took up residence inside a eukaryote about 2 billion years ago.
- The eukaryotic cells used their cytoskeletal elements to surround and engulf smaller prey.
- Instead of fusing with a lysosome and being digested, an engulfed bacterium began to live inside a eukaryotic cell.
- The engulfed cell survived by absorbing carbon molecules with high potential energy from the eukaryotic cell and oxidizing them, using oxygen as a final electron acceptor.
Describe five features of mitochondria that are consistent with the theory that mitochondria are endosymbiotic in origin.
- Mitochondria are about the size of an average bacterium and replicate by fission, as do bacteria.
- Mitochondria have their own ribosomes to manufacture their own proteins.
- Mitochondria have double membranes, consistent with the engulfing mechanism.
- Mitochondria have their own genomes with genes that code for the enzymes needed to replicate and transcribe their own genomes.
Provide three examples of the diversity of composition of hard outer coverings in protists.
- Diatoms are surrounded by a glass-like cell wall.
- Dinoflagellates have a cell wall made up of cellulose plates parabasalids have a unique internal support rod.
- euglenids have a collection of protein strips located just under the plasma membrane.
Multicellularity arose in many independent lineages of protists. Even some bacterial species can be said to be multicellular. In what eukaryote lineages did multicellularity independently arise?
Differentiate between ingestive feeding and absorptive feeding in protists.
- Ingesting packets of food compounds by ingesting food through plasma membrane or parasitizing other organisms.
- Others Performing photosynthesis.
Provide evidence for the endosymbiotic origin of the chloroplast in the Plantae lineage of protists.
- that the chloroplast, originated when a protist engulfed a cyanobacterium.
- the photosynthetic bacterium provided its eukaryotic host with oxygen and glucose in exchange for protection and access to light.
- evidence for an endosymbiotic origin for the chloroplast is even more persuasive than that for mitochondria.
Primary endosymbiosis is responsible for the chloroplasts in the Plantae lineage of eukaryotes. However, photosynthetic organelles also are found in some lineages of Excavata and Rhizaria; as well as in the Alveolata and Stramenopila. Explain the process of secondary endosymbiosis that is responsible for the existence of chloroplasts in these lineages.
Secondary endosymbiosis occurs when an organism engulfs a photosynthetic eukaryotic cell and retains its chloroplasts as intracellular symbionts. The chloroplasts from secondary endosymbiosis are surrounded by four membranes instead of two.
Describe three types of cellular motion in the protists.
- Amoeboid motion is a sliding movement observed in some protists that is accomplished by streaming of pseudopodia
- The other major mode of locomotion involves swimming via flagella or cilia.
Which Protists display these key features? Small sacs under plasma membrane, unicellular
Which Protists display these key features? Flagella covered with hairs, unicellular to multicellular
Which Protists display these key features? Excavated feeding groove, lost or reduced mitochondria
Which Protists display these key features? Lack cell walls, engulf food, pseudopodia
Which type of Protist is the following example from? Red Algae: aquatic phototrophs, absorb blue and green light Green Algae: aquatic phototrophs, absorb red light
Which type of Protist is the following example from? Amoebas: aquatic, unicellular Cellular Slime Moulds Plasmodial Slime Moulds: decomposers in forests
Which type of Protist is the following example from? Oomycota: filamentous detritivores, parasites, example Phytophthora Diatoms: unicellular phototrophs, silica cell wall Brown Algae: multicellular phototrophs, example kelp
Which type of Protist is the following example from? Diplomonadida: aquatic, example: Giardia sp. Euglenida: unicellular phototrophs and heterotrophs
Which type of Protist is the following example from? Cilata: unicellular, covered with cilia, example Paramecium Dinoflagellata: cause red tides Apicomplexa: malaria parasite Plasmodium
morphological features as __________________—shared, derived traits that are used to distinguish major monophyletic groups.
______________ have unusual flagella covered with hollow hair-like structures.
Based on diagnostic morphological characteristics the group ____________ includes the fungi and animals
Based on diagnostic morphological characteristics the group _________ includes the green plants
____________________ occurs when an organism engulfs a photosynthetic eukaryotic cell and retains its chloroplasts as intracellular symbionts.
The multicellular haploid form is called a _______________, because specialized cells in this form produce gametes by mitosis.
The multicellular diploid form is a _____________, because it has specialized cells that undergo meiosis to produce haploid cells called spores.
A ______ is a single cell that develops into an adult organism but is not a product of fusion by gametes.
Protists are a paraphyletic grouping that includes all eukaryotes except ____________________________
the land plants, fungi, and animals.
What key morphological innovations occurred as protists diversified
- the nuclear envelope,
- an array of structures that function in support and protection.
- the mitochondrion and chloroplast arose by endosymbiosis.
Can Protists reproduce both sexually and asexually?
___________ occurs when individuals of two different species live in physical contact
______________ occurs when an organism of one species lives inside an organism of another species.