Cyanobacteria and Autotrophic Protists (Algae) Flashcards

Flashcards for Bio23: Organismal and Environmental Biology Lab 13, focusing on cyanobacteria and autotrophic protists (algae).

What is Life History?

The study of how organisms allocate time and energy to maximize reproductive output, including habitat selection, energy acquisition strategies, and reproductive tactics. Key aspects include growth, reproduction, and survival strategies.

Elaborate on Cyanobacteria.

Prokaryotes known for their capability of oxygenic photosynthesis, similar to plants. They have a significant place in evolutionary history. Key genera include Anabaena, Nostoc, and Spirulina.

When do Cyanobacteria appear in the fossil record, and why is this significant?

Cyanobacteria appear at least 2.7 billion years ago in the fossil record, indicating they were among the earliest life forms capable of photosynthesis, influencing Earth's early atmosphere. Their presence is often marked by stromatolites.

What is Nitrogen Fixation and why is it important for certain organisms?

Nitrogen fixation is the conversion of atmospheric N2 to NH3 (ammonia), a biologically available form of nitrogen. This process is crucial for organisms that cannot directly use atmospheric nitrogen. The enzyme nitrogenase catalyzes this reaction.

Describe Heterocysts and their function.

Heterocysts are specialized cells in some cyanobacteria that are dedicated to nitrogen fixation. Structurally, they have thickened cell walls to create an anaerobic environment necessary for the nitrogenase enzyme to function. Common in genera like Nostoc and Anabaena.

What is Mucilage and what role does it play for cyanobacteria?

Mucilage is a polysaccharide substance that holds multiple cyanobacteria cells together, forming a protective matrix and aiding in colony formation. It can be structured in various forms, such as sheaths or capsules. This matrix protects against desiccation and UV radiation.

Explain what Trichomes are in the context of cyanobacteria.

Trichomes are filaments of cyanobacteria found in Sections III-V, representing a specific morphological arrangement among filamentous species. They consist of a linear series of cells attached end to end, and can be observed in genera like Oscillatoria.

What are Hormogonia and what is their purpose?

Hormogonia are short filaments released from the parent filament after programmed cell death in filamentous cyanobacteria, serving as a means of reproduction and dispersal. They are motile and can glide away from the parent colony. Often seen in Nostoc and Lyngbya.

Describe Section IV Cyanobacteria (e.g., Nostoc) and their key features.

Section IV Cyanobacteria, such as Nostoc, are filamentous cyanobacteria known for having specialized cells used for nitrogen fixation, particularly heterocysts. Their filaments are often arranged in mucilaginous colonies, easily visible under a microscope.

What are Algae?

Algae are an unnatural assemblage of photosynthetic organisms, typically simpler in morphology than plants. They are evolutionarily diverse and include both unicellular and multicellular forms, lacking complex structures like true roots, stems, and leaves. Examples include diatoms, dinoflagellates, and green algae.

How were algae traditionally divided into groups, and what is the limitation of this method?

Algae were traditionally divided based on distinctive plastid accessory pigments. However, this method does not reflect evolutionary relationships accurately due to convergent evolution of pigments. Modern classification uses molecular data.

What pigments are found in diatoms and how do they contribute to their color?

Diatoms contain chlorophyll and fucoxanthin. Fucoxanthin is a xanthophyll pigment that gives diatoms their characteristic golden-brown color. Structurally, they are characterized by their silica cell walls (frustules).

What are diatom cell walls made of, and what are the properties of this material?

Diatom cell walls are made of hydrated silica dioxide (SiO_2·nH2O), also known as opaline silica. This material is strong, transparent, and intricately patterned, providing protection and structural support. The cell walls are called frustules.

Describe the structure of a Frustule.

A Frustule consists of two halves (valves) that fit together like a Petri dish, forming the cell wall of a diatom. The valves are ornamented with pores and intricate patterns, known as striae, which are species-specific and visible under high magnification.

What accessory pigments give dinoflagellates their color?

Peridinin or fucoxanthin, both carotenoids, give dinoflagellates their distinctive olive-brown color. Many dinoflagellates also have two flagella, one longitudinal and one transverse, located in grooves called the sulcus and cingulum, respectively. Examples include Ceratium and Gymnodinium.

What class of accessory pigments makes red algae reddish, and what are their specific properties?

Phycobilins, including phycoerythrin and phycocyanin, are the accessory pigments that make red algae reddish. Phycoerythrin absorbs green light, which penetrates deeper into the water column. Red algae lack flagella and centrioles and have complex life cycles, with examples like Porphyra and Gracilaria.

What do red algae store carbohydrates as, and where is this storage located?

Red algae store carbohydrates as floridean starch, a type of glycogen-like polysaccharide. The storage is located outside the chloroplast in the cytoplasm. This starch differs from plant starch in its branching pattern.

What chloroplast pigment profile do green algae share with plants, and what does this indicate?

Green algae share chlorophyll a, chlorophyll b, beta-carotene, and xanthophylls with plants. This indicates a close evolutionary relationship and supports the theory of endosymbiosis.