23.2 - Characteristics of Protists

Question 1

Protist cell structure

Answer 1

• Most are microscopic & unicellular // some multi
• some are in colonies and behave almost like a group of free living cells
• some are multicellular
• some are multinucleated
• can be from 1 micrometer to a whole hectar
• can have animal or plant-like cell walls
• wall can be glassy and silica based, or it can be pellicles of interlocking proteins

Question 2

Protist Metabolism

Answer 2

• aerobic and anaerobic
• ameobas and other heterotrophs use phagocytosis to make phagosomes.
  - phagosomes mix with lysosomes that contain hydrolytic
  enzymes creating a phagolysosome
• mixotrophic protists also exist

Question 3

Motility

Answer 3

• some have 1 flagella (that rotates or whips)
• some have tiny cilia rows that cordinate a beat in order to swim
• some have pseudopodia (cytoplasmic extensions) in order to anchor
• some move through taxis. (movement dependent on stimulus)
  i.e = phototaxis moving through light

Question 4

Reproductions

Answer 4

• Asexual reproduction through binary fission
  can be longitudinal or transverse depending on the axis of orientation
• Can transform into sexual reproduction when in danger (such as no nutrients or bad temperature)
  transformation to sexual occurs maybe to make recombinant genes to create resistant “cysts” which are at a protective resting stage
• multiple fission (slime molds)
• budding

Question 5

Life Cycles

Answer 5

1) Parasytic
2) Animal like (unicellular haploid -> multicellular diploid)
3) Alternations of generations (plant-like multidiploid -> multidiploid)

Question 6

Habitats

Answer 6

• most live in an aquatic enviornment
• some are parasitic on land animals or plants
• some live in decaying organic matter and engage in the decomposing