Biology Chapter: Multicellular Organisms
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Questions and Answers

What is the primary reason organisms undergo cell division?

  • To consume nutrients more effectively
  • To increase their cell size significantly
  • To develop new organs and structures
  • To replace dead or damaged cells (correct)

How do asexual offspring differ from sexual offspring?

  • Asexual offspring inherit traits from both parents
  • Asexual offspring have half the genetic information of the parent
  • Asexual offspring are genetically identical to the parent (correct)
  • Asexual reproduction requires two parents

What is the average duration for a complete cell replacement in the human body?

  • Every 3 years
  • Every year
  • Every 5 years
  • Every 7 years (correct)

What phase comes after interphase in the cell cycle?

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

What structure forms during prophase of mitosis?

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

Which phase of the cell cycle involves DNA replication?

<p>S Phase (A)</p> Signup and view all the answers

What happens to brain and nerve cells after a few months of age?

<p>They are not produced again (D)</p> Signup and view all the answers

What are chromosomes comprised of?

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

Which of the following processes occurs during anaphase?

<p>Sister chromatids are pulled apart (B)</p> Signup and view all the answers

What is the purpose of mitosis?

<p>To produce two genetically identical daughter cells (B)</p> Signup and view all the answers

What is one characteristic of the G1 phase in interphase?

<p>Cells grow in size (A)</p> Signup and view all the answers

Which of the following statements is true about the liver cells?

<p>They rarely divide, but can in response to injury (C)</p> Signup and view all the answers

What directly follows mitosis in the cell cycle?

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

What is the key function of the cell's DNA?

<p>To direct everything within the cell (C)</p> Signup and view all the answers

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Flashcards

Multicellular Organism

An organism composed of multiple cells, with each cell operating independently yet cooperating for the organism's function.

Growth (Multicellular)

The process of increasing the number of cells in an organism through cell division, leading to growth.

Repair (Multicellular)

The replacement of damaged or dead cells through cell division, ensuring tissue repair and maintenance.

Asexual Reproduction

The process of producing offspring from a single parent.

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Sexual Reproduction

The process of producing offspring from the fusion of sex cells (gametes) from two parents.

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Cell Division

A vital process involving the division of a parent cell into two genetically identical daughter cells.

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DNA (Deoxyribonucleic Acid)

The DNA molecule found in the nucleus of a cell, containing the genetic instructions for an organism.

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Chromosomes

Long strands of DNA that carry genetic information in the nucleus of a cell.

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Cell Cycle

The continuous cycle of cell growth, replication, and division, with two main phases: interphase and mitosis.

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Interphase

The longest phase of the cell cycle where the cell grows, duplicates its DNA, and prepares for division.

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G1 Phase

A period of cell growth within interphase, where the cell increases in size and prepares for DNA replication.

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S Phase

A period in interphase where the cell replicates its DNA, creating two identical copies of each chromosome.

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G2 Phase

A period in interphase where the cell prepares for mitosis, synthesizing necessary proteins and organelles.

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Mitosis

The process of nuclear division in the cell cycle, where one cell divides into two genetically identical daughter cells.

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Cytokinesis

The physical division of the cytoplasm into two separate cells after mitosis, completing the cell cycle.

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Study Notes

Multicellular Organisms

  • Multicellular organisms are composed of more than one cell.
  • Cell division is crucial for growth, repair, and reproduction.

Growth

  • Organisms increase their cell number through cell division.
  • Humans develop from a single cell to 50-75 trillion cells.

Repair

  • Cell division replaces dead or damaged cells.
  • Millions of cells are shed and replaced constantly in areas like the intestines and skin.
  • On average, all cells are replaced approximately every 7 years (excluding nerve and cardiac cells).

Reproduction

  • Cell division is fundamental in both asexual and sexual reproduction.
  • Asexual Reproduction: offspring are genetically identical to the parent.
  • Sexual Reproduction: offspring inherit half their genetic information from each parent. Most multicellular organisms use this method.

Cell Division Rates

  • Rapid cell replacement occurs in hair, skin, nails, taste buds and the stomach lining.
  • Brain and nerve cells rarely regenerate after early development.
  • Liver cells can regenerate if damaged.

Chromosomes and DNA

  • DNA, located in the cell nucleus, contains the cell's genetic information.
  • DNA is organized into chromosomes; humans have 46 chromosomes (23 pairs).

The Cell Cycle

  • The cell cycle is divided into interphase and mitosis.
  • Interphase: The cell grows, duplicates its DNA, and prepares for mitosis. It has three distinct phases (G1, S, and G2).
    • G1: Cell growth occurs.
    • S: DNA replication occurs.
    • G2: Cell prepares for mitosis.
  • Mitosis: Cell division, resulting in two identical daughter cells.
    • Interphase: At the start of interphase, DNA exists as chromatin (thin, thread-like strands). Mitosis eventually results in the division of the cell's nucleus. Cytokinesis, the division of the cell cytoplasm, follows mitosis.
    • Mitosis Phases (PMAT):
      • Prophase: Chromatin condenses into chromosomes (each with two sister chromatids joined by a centromere).
      • Metaphase: Chromosomes align at the cell's center.
      • Anaphase: Sister chromatids separate and move to opposite poles.
      • Telophase: Chromosomes unwind back into chromatin. A new nuclear membrane forms around each set of chromosomes.
  • The entire process of mitosis takes about 80 minutes in most eukaryotic cells.

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Description

Explore the fascinating world of multicellular organisms in this quiz. Learn about the processes of growth, repair, and reproduction, and how cell division plays a vital role in these functions. Test your knowledge on the differences between asexual and sexual reproduction as well as the rates of cell division in various tissues.

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