Plant Structure and Cell Organization
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Questions and Answers

What is the role of auxin in plants?

  • Stimulates cell elongation (correct)
  • Promotes leaf abscission
  • Inhibits cell elongation
  • Facilitates seed germination

What aspect of plant behavior does the term 'tropism' specifically refer to?

  • Chemical communication between plant parts
  • Directed movement toward or away from stimuli
  • Random motion in response to a stimulus
  • The growth of an organism in response to a stimulus (correct)

Which hormone is primarily responsible for the ripening of fruit?

  • Ethylene (correct)
  • Abscisic acid
  • Auxin
  • Gibberellin

Which statement best describes 'kinesis' in response to stimuli?

<p>Random motion regardless of the stimulus (B)</p> Signup and view all the answers

What is the primary function of xylem in plants?

<p>Transport water and carbohydrates from leaves to other parts of the plant (C)</p> Signup and view all the answers

What is meant by positive taxis in organisms?

<p>Movement toward a stimulus (D)</p> Signup and view all the answers

Which of the following is NOT a function of abscisic acid in plants?

<p>Stimulates cell elongation (D)</p> Signup and view all the answers

What role do guard cells play in the functioning of stomata?

<p>They regulate the opening and closing of stomata (B)</p> Signup and view all the answers

What discovery did the Darwins make regarding plant behavior?

<p>The tip of the plant detects light (D)</p> Signup and view all the answers

Which process occurs within the chloroplasts of plants?

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

What initiates the opening of stomata in plants?

<p>Light stimulating guard cells to accumulate potassium ions (D)</p> Signup and view all the answers

Which of the following statements accurately describes the function of gibberellin?

<p>Affects fruit growth and seed germination (C)</p> Signup and view all the answers

What is the correct balanced equation for photosynthesis?

<p>6H2O + 6CO2 -&gt; C6H12O6 + 6O2 (D)</p> Signup and view all the answers

What is the primary product of photosynthesis?

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

What happens to guard cells when they accumulate potassium ions?

<p>Water enters by osmosis and they swell (A)</p> Signup and view all the answers

During cellular respiration, which of the following is produced?

<p>Water and carbon dioxide (A)</p> Signup and view all the answers

What distinguishes homologous chromosomes from each other?

<p>They can have different versions of the same gene. (D)</p> Signup and view all the answers

What is the primary purpose of meiosis in sexual reproduction?

<p>To produce haploid gametes. (C)</p> Signup and view all the answers

What is created during synapsis in meiosis?

<p>Tetrads are formed. (B)</p> Signup and view all the answers

How many daughter cells are produced at the end of meiosis?

<p>4 haploid cells. (C)</p> Signup and view all the answers

What is crossing over, and why is it important?

<p>A mechanism that increases genetic diversity. (B)</p> Signup and view all the answers

How do sex chromosomes differ between males and females?

<p>Males have XY chromosomes, and females have XX chromosomes. (C)</p> Signup and view all the answers

What happens to the chromosome number after fertilization?

<p>Doubles to restore diploid status. (D)</p> Signup and view all the answers

During which phase of meiosis do sister chromatids separate?

<p>Anaphase II. (A)</p> Signup and view all the answers

How does independent assortment contribute to genetic diversity?

<p>It allows for random orientation of chromosomes during meiosis. (D)</p> Signup and view all the answers

What is the total number of possible combinations of genetic variation from random fertilization, assuming 8.4 million sperm and 8.4 million eggs?

<p>Over 70 trillion (A)</p> Signup and view all the answers

What is the primary purpose of mitosis in multicellular organisms?

<p>To promote growth and repair tissues. (C)</p> Signup and view all the answers

During which phase of the cell cycle are sister chromatids formed?

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

What is the correct sequence of steps in the process of mitosis?

<p>Duplicate DNA, divide the chromosomes, divide the cell. (D)</p> Signup and view all the answers

What role does crossing over play in genetic diversity?

<p>It creates new combinations of alleles. (D)</p> Signup and view all the answers

Approximately what percentage of the cell cycle is spent in mitosis?

<p>10% (C)</p> Signup and view all the answers

What happens during the prophase stage of mitosis?

<p>Chromosomes condense and become visible. (A)</p> Signup and view all the answers

What phenomenon occurs when the cytoplasm shrinks and the plasma membrane pulls away from the cell wall in a hypertonic environment?

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

How does temperature affect transpiration in plants?

<p>Higher temperatures increase the rate of evaporation (B)</p> Signup and view all the answers

What is the primary function of phloem tissue in plants?

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

What term describes a plant's growth response toward a light source?

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

What is the role of companion cells in the pressure flow theory?

<p>Load sugar into the phloem (A)</p> Signup and view all the answers

Which of the following is a type of tropism that involves a response to gravity?

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

In what way does osmosis contribute to the transport of sugar in plants?

<p>It maintains a constant flow of food (C)</p> Signup and view all the answers

Which scientists first investigated the part of the plant that detects light for phototropism?

<p>Charles Darwin and Francis Darwin (A)</p> Signup and view all the answers

What is the primary function of palisade tissue cells in a leaf?

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

Which of the following best describes the role of stomata?

<p>Gas exchange and transpiration. (D)</p> Signup and view all the answers

What role does cohesion play in water transport within plants?

<p>It enables water molecules to cling to each other. (C)</p> Signup and view all the answers

How does root pressure contribute to water transport in plants?

<p>By creating positive pressure in the xylem. (C)</p> Signup and view all the answers

What is the primary purpose of spongy mesophyll tissue in a leaf?

<p>To facilitate gas exchange through diffusion. (B)</p> Signup and view all the answers

Which process creates the tension known as transpiration pull?

<p>Evaporation of water through stomata and lenticels. (A)</p> Signup and view all the answers

What characteristic allows water to travel upwards from roots to leaves against gravity?

<p>The combined effects of cohesion, adhesion, and transpiration. (B)</p> Signup and view all the answers

What type of tissue is primarily involved in transporting sugars produced during photosynthesis?

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

Flashcards

Photosynthesis

The process by which plants convert light energy into chemical energy stored in glucose.

Chlorophyll

The green pigment found in chloroplasts that absorbs light energy for photosynthesis.

Chloroplast

The site of photosynthesis in plant cells.

Stomata

Tiny pores on the surface of leaves that allow for gas exchange (CO2 in, O2 out).

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Guard Cells

Specialized cells that surround stomata and regulate their opening and closing.

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Cellular Respiration

The process by which plants break down glucose to release energy for cellular processes.

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Diffusion

The movement of molecules from an area of high concentration to an area of low concentration.

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Osmosis

The movement of water molecules across a semi-permeable membrane from an area of high water concentration to low water concentration.

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Phototropism

The bending of a plant in response to light.

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Hormone (in plants)

A chemical messenger produced in one part of a plant and transported to another, where it triggers a specific response.

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Auxin

A plant hormone that stimulates cell elongation, primarily responsible for phototropic responses.

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Taxis

A directed movement by an organism towards or away from a stimulus.

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Positive Taxis

Movement towards a stimulus.

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Negative taxis

Movement away from a stimulus.

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Kinesis

Random, undirected movement in response to a stimulus.

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Tropisms

An organism's automatic, directed movement in response to a stimulus, such as light, chemicals, or gravity.

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Independent Assortment

The random orientation of homologous chromosomes during meiosis I, resulting in diverse gametes.

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Random Fertilization

The random union of any sperm with any egg, further contributing to genetic diversity.

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Crossing Over

The exchange of genetic material between homologous chromosomes during meiosis I, creating unique combinations of alleles.

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Mitosis

The process by which a single cell divides into two identical daughter cells, crucial for growth, repair, and asexual reproduction.

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Interphase

The phase of the cell cycle where the cell prepares for division, including DNA replication and organelle production.

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Prophase

The stage of mitosis where replicated chromosomes condense and become visible, the nuclear envelope breaks down, and spindle fibers form.

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Metaphase

The stage of mitosis where chromosomes align at the center of the cell, attached to spindle fibers.

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Anaphase

The stage of mitosis where sister chromatids separate and move to opposite poles of the cell.

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Homologous Chromosomes

Pairs of chromosomes that are the same length and carry the same genes in the same location. They may have different versions of the same gene.

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Gametes

Specialized cells involved in sexual reproduction. They contain only half the number of chromosomes of a normal cell.

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Meiosis

The process of cell division that produces four haploid gametes (sex cells).

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Meiosis I

The first stage of meiosis where homologous chromosomes pairs are separated. This results in two daughter cells, each with half the number of chromosomes as the original cell.

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Meiosis II

The second stage of meiosis where sister chromatids are separated. This results in four haploid daughter cells, each with half the number of chromosomes as the original cell.

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Tetrad

A structure formed during prophase I of meiosis where homologous chromosomes pair up and exchange genetic material.

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Synapsis

The pairing of homologous chromosomes during Prophase I of meiosis.

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Water Transport in Xylem

The process where water moves up the xylem of a plant, aided by factors like cohesion, adhesion, and root pressure.

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Transpiration

A process where plants lose water vapor from their leaves, mainly through tiny pores called stomata. The rate increases with higher temperatures, leading to faster water movement in the xylem.

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Plasmolysis

The shrinking of a plant cell's cytoplasm and plasma membrane away from the cell wall due to the loss of water to a hypertonic environment (a solution with a higher concentration of solutes than the cell).

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Phloem

The tissue that transports sugars from the site of photosynthesis (the leaves) to other parts of the plant (the sinks).

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Pressure Flow Theory

The theory explaining sugar transport in plants. It involves the active transport of sugars into the phloem, creating a high pressure that pushes the sugar solution towards the sinks.

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Gravitropism / Geotropism

A plant's response to gravity, resulting in growth downwards (positive) or upwards (negative).

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What is Transpiration?

The process of water vapor leaving the leaf through tiny pores called stomata.

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How do stomata close during drought?

Guard cells are specialized cells surrounding stomata that control their opening and closing. When water is scarce, guard cells become limp and close the stomata to prevent water loss.

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What is Mesophyll?

Mesophyll is the ground tissue inside a leaf, made up of thin-walled cells containing chloroplasts. It's where photosynthesis takes place.

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Where are Palisade Tissue Cells found?

Palisade tissue cells are found below the upper epidermis of a leaf. They are arranged in a way that allows them to capture sunlight for photosynthesis.

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What is Spongy Mesophyll?

Spongy mesophyll tissue is found below the palisade tissue. Its loose structure allows for easy gas exchange within the leaf.

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What is Cohesion?

Cohesion is the attraction between water molecules due to their polar nature (positive and negative ends). It allows water to cling together.

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What is Adhesion?

Adhesion is the attraction between water molecules and other substances. It helps water climb up the plant.

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What is Root Pressure?

Root pressure is the positive pressure created when water is drawn into root cells due to higher solute concentration. It helps push water up the xylem.

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Study Notes

Cell Specialization and Organization

  • Unicellular vs. multicellular organisms: specialized cells in multicellular organisms are more efficient at performing specific tasks; single-celled organisms must multi-task.
  • Size: surface area-to-volume ratio limits growth in unicellular organisms; efficient transport systems allow larger size in multicellular organisms.
  • Interdependence of cells: a multicellular organism does not die if a single cell fails; a malfunctioning cell within a multicellular organism can cause problems for the entire organism.

Plant Structure – Cells, Tissues, and Systems

  • Tissues: groups of cells performing similar functions form tissues
  • Organs: tissues performing similar functions group to form organs
  • Systems: organs working together as interconnected parts form a system
  • Plant systems: the shoot system is above ground; the root system is below ground.

Plant Tissues

  • Dermal tissue: outer layer, exchanges matter and gases with its environment, protects the plant from disease or microorganism attack
  • Ground tissue: beneath the epidermis, majority of plant, provides strength and support, involved in many plant functions
  • Vascular tissue: responsible for transporting materials, xylem conducts water and minerals from roots to leaves, phloem transports carbohydrates and water from leaves to other parts of the plant

Specialization in Plants

  • Cells become specialized to perform particular functions and produce needed products
  • Examples include Root Hairs (water and mineral absorption), Formation of Cuticle, Guard cells (gas exchange), Xylem

The Chloroplast: A Unique Organelle

  • Chloroplasts contain chlorophyll.
  • Chloroplasts are found in the leaves and stems
  • Chloroplasts are the site where photosynthesis occurs
  • Photosynthesis uses light energy, carbon dioxide, and water to produce sugars; release oxygen.

Cellular Respiration (Plants)

  • Breakdown of glucose to release energy that cells can use.
  • Word equation: glucose + oxygen → carbon dioxide + water + energy.
  • Balanced equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy.

Leaf Tissues and Gas Exchange

  • Guard cells: regulate gas exchange through pores called stomata (regulates carbon dioxide and oxygen intake through diffusion)
  • Stomata: mostly found under the leaf epidermis, facilitating gas exchange (CO2 and O2)

Ground Tissue (Leaves)

  • Mesophyll: specialized ground tissue in a leaf, made up of thin-walled cells containing chloroplasts
  • Palisade tissue cells: located under the upper epidermis, arranged parallel to allow exposure to sunlight, responsible for photosynthesis.
  • Spongy mesophyll tissue: increased space between cells allows for gas exchange throughout the leaf.

Vascular Tissue

  • Provides the leaf with water for transpiration and photosynthesis, and then removes sugars produced in photosynthesis.
  • Xylem and phloem tissues are bunched together in a vascular bundle, aiding in the transport of water and nutrients.
  • Other sites of gas exchange in plants, such as stomata on leaves and lenticels on stems, provide pathways for gas exchange.

Transport in Plants

  • Cohesion: water molecules attract one another, due to polar nature
  • Adhesion: water molecules attract other substances, such as xylem walls
  • Root pressure: a result of active transport pushing water up the roots
  • Transpiration: the driving force for water transport in plants
  • Tension-cohesion theory: explains the upward movement of water from roots to leaves.

From Root to Leaf (Transport in Plants):

  • Transpiration through stomata and lenticels.
  • Cohesion and adhesion of water molecules.
  • Root pressure.
  • Effect of tonicity on plants (Plasmolysis): shrinking of the cytoplasm and plasma membrane due to water outflow from the cell.
  • Transport of sugars from leaves to other parts of the plant via phloem tissue (source to sink)
  • Pressure flow theory: loading of sugars into the phloem at the source, water moves into the sieve cells by osmosis, generating pressure, pushing water and sugars to the sink

Control Systems (Plants)

  • Plant responses to stimuli, including water, carbon dioxide, and light; response in terms of growth.
  • Examples such as phototropism (response to light), geotropism (response to gravity), and hydrotropism (response to water)

Taxis and Kinesis

  • Taxis: an automatic, directed movement toward or away from a stimulus.
  • Kinesis: a random, undirected motion in response to a stimulus
  • Examples of taxis: Euglena moving towards light; male moths towards pheromones; fish swimming upstream.
  • Examples of kinesis: Cockroaches scattering when light turns on; E. coli randomly moving when nutrients are depleted.

Taxonomy – Kingdoms of Life

  • Taxonomy: classification of living organisms in a hierarchical structure.
  • Kingdoms are organized into Domains, which are now grouped into domains: Bacteria, Archaea, and Eukarya, based on their genetic makeup.
  • Prokaryotic cells: bacteria and archaea
  • Eukaryotic cells: fungi, plants, animals, protists
  • Key difference between prokaryotic and eukaryotic cells: Eukaryotic cells have a nucleus and other membrane-bound organelles.

Meiosis

  • The process of cell division that produces gametes (sex cells) with half the number of chromosomes as the parent cell.
  • Four haploid daughter cells are the result.
  • Meiosis involves two rounds of cell division: Meiosis I and Meiosis II. − Events contributing to genetic diversity: independent assortment, random fertilization, crossing over.
  • Stages of meiosis.

Mitosis

  • The process of cell division that produces two identical daughter cells from a single parent cell.
  • Steps of mitosis: interphase, prophase, metaphase, anaphase, and telophase / cytokinesis

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Explore the fascinating concepts of cell specialization and the structure of plants in this quiz. Understand the differences between unicellular and multicellular organisms, the interdependence of cells, and the organization of plant tissues, organs, and systems. Test your knowledge on how these elements contribute to plant development and functionality.

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