MC2: The eukaryotes Flashcards
What are the two key differences between a prokaryote and a eukaryote?
Prokaryotes have a nuceloid and no organelles
Eukaryotes have a nucleus and membrane-bounds organelles
How do unicellular eukaryotes reproduce?
Asexually by mitosis when in favourable conditions
Sexually by meiosis and syngamy under stressful conditions (e.g. nutrient limitations and DNA damage)
Who invented the first microscope? Why?
Antonie van Leeuwenhoek whilst trying to look at the quality of thread
What discoveries did Antonie van Leeuwenhoek make? When?
- 1674: protists (known as infusoria) in lakes
- 1676: the vacuole of the cell
- 1677: spermatozoa
- 1682: the banded pattern of muscular fibres
- 1683: bacteria such as Selenomonads from the human mouth
What were protista?
The ancestor of plants, fungi and animals
What is a monophyletic group?
A group containing a common ancestor and all of its descendents
What is a paraphyletic group?
A group that contains its most recent common ancestor, but does not contain all the descendents of that ancestor
What is a polyphletic group?
A group that does not contain the most recent common ancester of all its members
What defines a protist?
- “A eukaryotic microbe that is not an animal, plant, or (true) fungus”
- Simple and primitive organisms
- Unicellular
- Motile and lack cell walls
- Taxonomy still changing
What are the three major types of protist?
- Fungus-like slime/water moulds, e.g. slime mould
- Animal-like protozoa, e.g. amoeba
- Plant-like algae, e.g. Euglena
How do protists differ from:
- prokaryotes
- animals
- fungi?
- The cells have features of eukaryotes and cells are bigger
- They are always unicellular
- They are motile and lack cell walls
Where do all free-living protists live?
In water
What type of symmetry do protists display?
Asymmetry or radial/bilateral symmetry
What are the different types of protist locomotion?
- Finger-like pseudopodia, e.g. amoeba
- Whip-like flagella, e.g. Euglena
- Hairy cilia (used to direct food into mouth), e.g. Paramoecium
- By contraction
- No motion
Define ‘holozoic’.
A form of nutrition where a whole particle is taken in via the vacuole
Define ‘mixotrophic’.
A form of nutrition where particles are taken in and photosynthesised
Define ‘parasitic’ in terms of nutrition
A form of nutrition involving feeding off the host organism
Define ‘saprozoic’
A form of nutrition where protists live on decaying matter
What are the four main types of nutrition of protists?
- Holozoic
- Mixotrophic
- Parasitic
- Saprozoic
Is digestion in protists intra- or extracellular?
Intracellular, occuring in the food vacuole
How do respiration and excretion take place in protists?
By the exchange of gases through the body surface
Some excretion occurs through contractile vacuole
What is a protist’s nitrogenous waste and how is it excreted?
Ammonia, excreted through urea
How do some fresh-water protozoa get rid of excess water?
Through contractile vacuoles
What caused the Irish potato famine?
Phytophthora infestans came to Europe in the 1800s and caused the potato famine of 1845
It is an oomycete and is very flexible and adaptable, and finds ways to escape plant resistance
Researchers and plant-breeders are developing a resistance involving multiple genes to slow the spread of the fungus
Why has Dictyostelium discoideum been studied lots?
It is a cellular slime mould that has been used as a model for studying intercellular communication and cooperation amongst microbes
It is used as a model to understand human muscle
How many species of Plasmodium parasite cause malaria in humans? Name these species.
Five:
- P. falciparum
- P. vivax
- P. ovale
- P. malariae
- P. knowlesi
How can free-living aquatic amoeba cause disease in humans?
They can either eat bacteria or other amoeba and can farm or house bacterial pathogens which cause disease
Which type of protist fixes up to half the CO2 in the oceans? How?
Plant-like protists
They photosynthesise using chlorophyll and other pigments
What are diatoms and what is their structure?
- Producers in the food chain that are structured like a petri dish
- They have walls made of silica and pectin
What is the role of diatoms in the oceans?
They fix carbon and monitor water status
What are dinoflagellates?
- Flagellated primarily marine algae
- Phylogenetic relatives of several groups of protozoa
- Some are free-living, others are symbionts
- Some are toxic and cause ‘red tides’; others have bioluminescence
What are microscopic animals or micro-animals?
Multicellular organisms that are not vertebrates
What are the two groups of microscopic animals? Give examples of each.
-
Arthropods
- e.g. dust mites, spider mites
-
Crustaceans
- e.g. copepods, cladocera
What are rotifiers? Where are they found?
Filter-feeders found in fresh water
What are fungal cell walls made of?
Chitin
What are moulds?
Forms of filamentous fungi that are widespread in nature
Most are obligate aerobes
Which antibiotic comes from a fungus? Name the fungus.
Penicillin from Penicillium notatum
What are yeasts?
Unicellular fungi, mostly ascomycetes, that are larger than bacterial cells
Where do yeasts flourish?
Where sugars are present
What is the most comercially important yeast?
Saccharomyces cerevisiae
