Lecture 10: Eukaryotes and Protists

What is a Protist?

A Protist refers to most of the eukaryotes, excluding plants, animals, and fungi. It is a paraphyletic group.

What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have a nucleus, undergo mitosis and meiosis, have organelles like mitochondria and chloroplasts, linear chromosomes, and can be diploid.

What is the endosymbiotic theory?

The endosymbiotic theory hypothesizes that some early eukaryotic cells engulfed prokaryotic cells, which then became integrated as organelles like mitochondria and chloroplasts.

How does Giardia lamblia contribute to understanding the origin of the nucleus?

Giardia has two haploid nuclei, suggesting a possible evolutionary path from haploid prokaryotes to primitive eukaryotes with diploid nuclei.

What roles do mitochondria and chloroplasts serve in eukaryotic cells?

Mitochondria are responsible for cellular respiration, while chloroplasts are the sites of photosynthesis.

What are some characteristics of Foraminifera?

Foraminifera are single-celled, heterotrophic, with calcium carbonate shells, and have an extensive fossil record.

What is significant about Apicomplexans?

Apicomplexans, such as Plasmodium falciparum, are parasitic protozoa that cause malaria, a major global health concern.

What leads to a 'red tide' in dinoflagellates?

A 'red tide' occurs when certain species of dinoflagellates proliferate rapidly under favorable conditions, which can produce toxins harmful to other marine species.

What type of organisms are algae and their ecological importance?

Algae are primarily autotrophic, mostly aquatic, 'plant-like' protists that play a crucial role in carbon fixation and oxygen production.

What defines the alternation of generations in algal life cycles?

Alternation of generations involves a life cycle that includes both a multicellular diploid phase (sporophyte) and a multicellular haploid phase (gametophyte).

Why is water essential for the reproduction of algae?

Water is crucial because the motile spores and gametes require it for swimming and because it provides support and nutrients.

What is a key difference in reproduction between eukaryotes and prokaryotes?

Eukaryotes undergo meiosis to form gametes with distinct sexes, while prokaryotes reproduce asexually by fission.

What is the significance of chlorophyll in eukaryotic autotrophs?

Chlorophyll 'a' captures light energy for photosynthesis, and many algae also contain other pigments that distinguish different types.

How do multicellularity and chlorophyll relate to the evolution of plants?

Multicellularity in certain protists likely evolved independently; plants evolved from green algal ancestors that share similarities in chlorophyll usage.

What are the implications of the two-fold cost of sex in eukaryotes?

The two-fold cost refers to the need for two parents to produce offspring, which raises questions about the evolutionary advantage of sexual reproduction despite its costs.

What are the two main types of eukaryotic organisms?

The two main types of eukaryotic organisms are unicellular (like protists) and multicellular (like plants, animals, and fungi).

What is the role of pseudopodia in some protists?

Pseudopodia are extensions of the cell membrane that allow protists to move and capture food through a process called phagocytosis.

What ecological role do zooplankton play?

Zooplankton are small, drifting organisms that are vital in aquatic food chains, serving as primary consumers that feed on phytoplankton.

How do diatoms contribute to the environment?

Diatoms are a major type of phytoplankton that are key producers in aquatic ecosystems, contributing to carbon fixation and oxygen production.

What are the main forms of reproduction in protists?

Protists can reproduce asexually through binary fission or sexually through processes like conjugation or the formation of gametes.

Why are slime molds studied in biology?

Slime molds are studied for their unique life cycles and their ability to demonstrate collective behavior and problem-solving abilities.

What is phytoplankton and its significance?

Phytoplankton are microscopic algae that float in water and are essential for producing oxygen and forming the base of aquatic food webs.

What is the function of the contractile vacuole in protists?

The contractile vacuole helps maintain osmotic balance by expelling excess water from the cells of certain freshwater protists.

What role does the cell wall play in protists?

The cell wall in some protists provides structure and protection, and may aid in maintaining shape, as seen in diatoms and some algae.

What are the ecological impacts of harmful algal blooms?

Harmful algal blooms can produce toxins, deplete oxygen levels, and cause significant harm to marine life and human health.