Biology Chapter on Cell Walls and Volvox
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Questions and Answers

What material is primarily found in the cell wall?

  • Cellulose (correct)
  • Pectin
  • Lignin
  • Chitin

What is the structure of the cell wall at the anterior end known as?

  • Cellular membrane
  • Cytoplasmic extension
  • Apical papilla (correct)
  • Surface layer

Which characteristic is true about the exterior of the cell wall?

  • It is covered in spikes.
  • It is thick and rough.
  • It is smooth and thin. (correct)
  • It is porous and flexible.

How many layers does the cell wall have?

<p>Many layers (A)</p> Signup and view all the answers

What can be inferred about the structure of the cell wall?

<p>It is complex in structure. (B)</p> Signup and view all the answers

What is the typical shape of the thallus?

<p>Round, oval, or pear-shaped (B)</p> Signup and view all the answers

What is a characteristic feature of the cell wall?

<p>Thin, firm, and made of rigid cellulose (C)</p> Signup and view all the answers

What shape is the chloroplast and what unique feature does it have?

<p>Cup-shaped; has a red pigmented eye spot (B)</p> Signup and view all the answers

What is the function of the red pigmented eye spot?

<p>To sense light and aid in photoreception (B)</p> Signup and view all the answers

Which statement about the thallus is true?

<p>It is distinguished by a narrow anterior and a broad posterior end. (D)</p> Signup and view all the answers

What enables the Volvox cells to move through the water?

<p>Two flagella (B)</p> Signup and view all the answers

How do Volvox cells obtain their food?

<p>Through photosynthesis (B)</p> Signup and view all the answers

Which cellular structure is NOT involved in Volvox cell movement?

<p>Chloroplasts (C)</p> Signup and view all the answers

In what process do Volvox cells use chlorophyll?

<p>Photosynthesis (D)</p> Signup and view all the answers

Which characteristic is unique to Volvox cells compared to many other algae?

<p>Ability to form colonies (D)</p> Signup and view all the answers

What is the typical range of thylakoids that can join within a chloroplast?

<p>Two to six (C)</p> Signup and view all the answers

What is a unique feature of the pyrenoid in chloroplasts?

<p>It is a small compartment found only in algae. (C)</p> Signup and view all the answers

How many thylakoids typically associate with each other in chloroplasts?

<p>Two to six (C)</p> Signup and view all the answers

Which statement about the pyrenoid is correct?

<p>It is a unique compartment in algae's chloroplasts. (C)</p> Signup and view all the answers

What role do thylakoids play in the chloroplast?

<p>They are involved in photosynthesis. (B)</p> Signup and view all the answers

What is the primary function of the chloroplast in plant cells?

<p>To convert sunlight into energy and sugars (B)</p> Signup and view all the answers

What role do pyrenoids play in the Chlamydomonas?

<p>Helping with the synthesis of starch (B)</p> Signup and view all the answers

Which process is primarily associated with chloroplasts?

<p>Photosynthesis (B)</p> Signup and view all the answers

In addition to starch synthesis, what other function is associated with the chloroplast?

<p>Light absorption (B)</p> Signup and view all the answers

What is the relationship between chloroplasts and pyrenoids in Chlamydomonas?

<p>Chloroplasts facilitate photosynthesis, and pyrenoids help synthesize starch within them (D)</p> Signup and view all the answers

What is the primary function of the thick, ornamented walls secreted by the zygote?

<p>To protect the zygote from environmental stress. (B)</p> Signup and view all the answers

What type of spore is a zygote classified as?

<p>Diploid spore (2n) (A)</p> Signup and view all the answers

What substances accumulate within the zygote as it develops?

<p>Starches and oils (A)</p> Signup and view all the answers

Which statement about the zygote is true?

<p>It can survive in harsh environments due to its protective walls. (C)</p> Signup and view all the answers

Which characteristic distinguishes zygotes from other types of spores?

<p>Zygotes are specifically diploid with a high starch content. (C)</p> Signup and view all the answers

Flashcards

Thallus Shape

The overall shape of a unicellular alga, such as Chlamydomonas.

Cell Wall

A rigid structure that surrounds the cell of a Chlamydomonas alga.

Cell Wall Composition

A thin, firm layer made up of cellulose that surrounds the cell of Chlamydomonas.

Chloroplast

A green organelle responsible for photosynthesis in Chlamydomonas.

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Stigma

A light-sensitive structure in Chlamydomonas that helps the alga sense light for photosynthesis.

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Cell Wall Exterior

The smooth and thin outermost part of the Chlamydomonas cell wall.

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Cellulose

A strong structural component found in the Chlamydomonas cell wall, providing rigidity.

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Apical Papilla

A projection extending from the cell wall at the front of the Chlamydomonas cell.

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Cell Wall Complexity

The cell wall of Chlamydomonas has numerous layers, forming a complex structure.

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Pyrenoids

A specific structure found in Chlamydomonas that helps with the synthesis of starch.

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Photosynthesis

The process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen.

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Chlamydomonas

A single-celled green alga that has a distinctive cup-shaped chloroplast.

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Starch

Starch is a complex carbohydrate that acts as a store of energy for the alga.

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Thylakoid Joining

The number of thylakoids that join together within a chloroplast can vary, typically ranging from two to six.

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Carbon Fixation

The process by which carbon dioxide is converted into organic compounds, a key stage of photosynthesis.

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Algal Photosynthesis

A type of photosynthesis that is uniquely found in algae, where carbon fixation occurs in pyrenoids.

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Zygote or Zygospore

A resting stage of an alga, formed when two gametes fuse.

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Ornamented Walls

A thick, protective outer layer around a zygote, made of multiple layers.

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Starches and Oils

A type of carbohydrate that provides a energy reserve for the zygote.

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Diploid (2n)

The condition of containing two sets of chromosomes, as in a zygote formed by combining two gametes.

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Resting Spore

A resting spore that can survive harsh conditions and later develop into a new alga.

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How do Volvox cells move?

Volvox are colonial organisms, which means they are a group of similar cells joined together. They are able to move through the water by using two flagella on each cell.

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How do Volvox cells obtain food?

Volvox cells contain chlorophyll and are able to produce their own food through photosynthesis.

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Volvox cells are what type of cells?

Volvox cells are similar to plant cells. They are able to make their own food. These cells are also called 'autotrophs.'

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What is a Volvox?

Volvox are spherical colonies of green algae. The cells have a similar structure to the single-celled Chlamydomonas alga.

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What are the two main characteristics of Volvox cells?

Volvox cells are able to make their own food through photosynthesis and have flagella for movement.

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Study Notes

Chlorophyta (Green Algae)

  • Green algae are unicellular, colonial, or multicellular.
  • Pigments include chlorophyll a, b, and carotenoids.
  • Most green algae possess flagella.
  • Cell walls are composed of cellulose.
  • Share characteristics with plants, including similar pigments, reserve products, and cell walls.
  • RNA sequencing suggests plants evolved from ancestral green algae.
  • Examples include Chlamydomonas (unicellular), Desmids, Volvox (colonial), Spirogyra (filamentous), and Ulva (sheet-like multicellular).

Chlamydomonas sp.

  • Unicellular, flagellated green alga.
  • Thallus shape: round, oval, or pear-shaped with a narrow anterior and broad posterior end.
  • Thin, firm cell wall made of cellulose.
  • Cup-shaped chloroplast with a red eyespot (stigma), considered a light-sensitive/photoreceptive organ.
  • Two equal anterior flagella and two anterior contractile vacuoles for osmoregulation and excretion.
  • A pyrenoid body that synthesizes starch (converted to oil).
  • May obtain some nutrients from surrounding water.
  • Cell Structure: Cilia, cell wall, plasma membrane, cytoplasm, Golgi bodies

Chlamydomonas Reproduction

  • Asexual: The cell divides mitotically within the cell wall, creating 2–4 daughter cells.
  • Sexual: Reproduction is isogamous, anisogamous, or oogamous.
  • Isogamy: Gametes are similar.
  • Anisogamy: Gametes differ in size.
  • Oogamy: A non-motile female gamete (egg) is present.

Volvox sp.

  • Mobile colony of green algae with 500–50,000 cells contained within a gelatinous wall.
  • Spherical or oval hollow colony.
  • Cells possess two flagella for movement.
  • Chlorophyll for photosynthetic food production.

Volvox Reproduction

  • Asexual: Gonidia develop in posterior part of colony which divide to produce daughter colonies.
  • Sexual: Oogamous, involving specialized male and female reproductive cells (antheridia and oogonia)

Spirogyra sp.

  • Multicellular, filamentous green alga with a mucilagenous sheath.
  • Cylindrical cells that are arranged end-to-end.
  • Cell walls are composed of cellulose and pectin.
  • Cytoplasm is peripheral with a central vacuole.
  • Ribbon-shaped chloroplasts are typically spiral.
  • Each chloroplast possesses numerous pyrenoids.
  • Single nucleus in the center of the vacuole.

Spirogyra Reproduction

  • Asexual: Simple mitotic division to create new cells. Favors favorable conditions.
  • Sexual: Conjugation; conjugation tubes form between filaments. Contents of one cell pass through to fuse with another resulting in a diploid zygote. The zygote forms a resistant zygospore and later produces new filaments under favorable conditions.

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Related Documents

Lecture 6: Chlorophyta (Green Algae) PDF

Description

Test your knowledge on the structure and function of cell walls, particularly in Volvox. This quiz covers key characteristics, cellular structures, and the unique features of chloroplasts. Dive into the fascinating world of plant biology and test your understanding!

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