Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

● Protists are first group of eukaryotes
○ Domain Eukarya is the third domain on the tree of life
● Eukaryotes range from single-celled organisms the size of bacteria to sequoia trees and
blue whales (largest animal that has ever lived, bigger than dinosaurs)
● Eukaryotes are diverse, yet share fundamental features that distinguish them from
bacteria and archaea:
○ Most are large, have more organelles and a more extensive cytoskeleton
■ Cytoskeleton: Made of proteins, basically gives cell its shape
○ A nuclear envelope
■ Separates nucleus from cytoplasm
○ Multicellularity evolved multiple times
○ Asexual and sexual reproduction

Protists
● All eukaryotes except land plants, fungi, and animals
● Tend to live in environments where they are surrounded by water most of the time
○ Generally live in aquatic environments
■ Open ocean (microscopic protists such as diatoms), shallow coastal waters
(gigantic protists, such as kelp)
● Have big effects on us and the planet
​ ○ Phytophthora infestans (generally speaking called a ​water mold​)
■ Caused Irish potato famine in 1845
■ Killed off potato harvests, about 1 million people died
○ Malaria is one of the world’s most chronic public health problems
■ Caused by five species of the parasitic protist ​Plasmodium
● Transferred to humans from mosquitoes
■ The cell types that make up each stage of the ​Plasmodium’s life cycle are
​
each specialized for infecting a specific host cell
■ U
...
is malaria free, so we don’t really think about it
■ *Look at both pics on next page*

○ Harmful Algal Blooms
■ A bloom occurs when a unicellular species’ population grows rapidly and
reaches high densities in an aquatic environment
● Caused by photosynthetic, toxin-producing protists called
dinoflagellates
● Harmful to humans because toxins build up in clams and other
shellfish
○ Shellfish are typically not harmed
○ But humans eating shellfish can be poisoned
Protists Play a Key Role in Aquatic Food Chain
● A ​food chain​ describes nutritional relationships among organisms
○ Many of the species at the base of food chains in aquatic environments are protists
○ Plankton-​ diatoms and other small organisms that drift in the open oceans or
lakes
■ Photosynthetic
■ CO2 + sunlight → food (glucose)
○ Protists represent just 10% of the named eukaryotic species, but they are
extraordinarily abundant
○ Primary producers​- species that produce chemical energy by photosynthesis
Secondary consumers → primary consumers → primary producers
○ Production by marine protists represents almost half of the total carbon dioxide
that is fixed on Earth

● *look at different trees in notes slides 21-23*
What Morphological Innovations Evolved in Protists?
● The earliest eukaryotes were probably single-celled organisms with:
○ Mitochondria
○ A nucleus and endomembrane system
○ A cytoskeleton
○ No cell wall
● These cells probably swam using a ​novel type of flagellum

● Bacteria flagellum: made up of protein called flagellin
● Eukaryotic flagellum: made up of long strands called microtubules; within those are
dynein
Endosymbiosis and the Origin of the Mitochondrion
● Mitochondria-​ organelles that generate ATP
● Endosymbiosis theory​- mitochondria originated when a bacterial cell took up residence
inside another cell about 2 billion years ago

○ Symbiosis-​ when individuals of two different species live in physical contact
○ Endosymbiosis-​ when an organism of one species lives ​inside​ the cells of an
organism of another species
● Mitochondria and bacteria similarities
○ Reproduce independently
■ Split, and reproduce another copy of themselves
○ Have their own ribosomes (for protein synthesis)
○ Genome (look a lot like plasmids found in bacteria)
■ Separate DNA from nucleus inside cell
○ Double membrane
■ Outer membrane
■ Inner membrane
○ Genes in mitochondria are more similar to bacteria than the eukaryotic cell it
resides in
● The Endosymbiosis Theory
○ Start with separate bacterium and host cell
○ Then the host cell surrounds and engulfs bacterium
○ Bacterium then lives within host cell
○ Endosymbiosis: host cell supplies bacterium with protection and carbon
compounds
...
Asexual Reproduction
○ Meiosis is adaptive because genetically variable offspring may be able to thrive if
the environment changes
○ The genotypes of many parasites and pathogens evolve very quickly
■ Natural selection favors host individuals with new genotypes that may be
able to resist these parasites and pathogens
○ Many biologists view sexual reproduction as an adaptation to fight disease
Life Cycles
● A life cycle describes the sequence of events that occur as an individual's grow, mature,
and reproduce
● Haploid v

---