Intro to Animals — Ch. 33 Part 2
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이 덱의 플래시카드 (23)

  • What is the ploidy of most adult animals?

    • Diploid (2n)
    life-cycle ploidy

  • Which mode of reproduction is most common in animals?

    • Sexual reproduction
    reproduction animals

  • What type of meiosis do most animals exhibit?

    • Gametic meiosis
    meiosis gametes

  • What is the chromosome equation for fertilization?

    • \(n + n = 2n\)
    fertilization ploidy

  • When do most animal tissues form?

    • During embryogenesis
    embryogenesis development

  • What early embryonic process produces an eight-cell stage after fertilization?

    • Cleavage (early embryonic cell divisions)

    Animal life cycle diagram

    cleavage embryology

  • Name the three primary germ layers formed during gastrulation.

    • Ectoderm
    • Endoderm
    • Mesoderm
    germ-layers gastrulation

  • Are most animals diploid or haploid and what is their common mode of reproduction?

    • Most animals are diploid
    • Reproduction: sexual
    life-cycle reproduction

  • What type of meiosis is listed for animals?

    • Gametic meiosis
    meiosis genetics

  • What does the eight-cell stage undergo to form the next embryonic structure?

    • Further cleavage to form a blastula
    cleavage embryology

  • What is a blastula's basic structure?

    • A hollow ball of cells with an internal cavity called the blastocoel
    blastula embryology

  • What is the typical ploidy of adult animals that reproduce sexually?

    Diploid

    life-cycle ploidy

  • What type of meiosis do animals with sexual reproduction undergo?

    Gametic meiosis

    meiosis reproduction

  • Write the fertilization chromosome equation for gamete fusion.

    \(n + n = 2n\)

    fertilization chromosomes

  • Which early embryonic stage follows cleavage and precedes gastrulation?

    Blastula formation

    embryogenesis stages

  • What key event occurs during gastrulation in early embryos?

    Formation of a blastopore and initial germ-layer formation

    gastrulation embryology

  • Name the three primary germ layers formed during early embryogenesis.

    • Ectoderm
    • Endoderm
    • Mesoderm

    Diagram showing blastula to early gastrula, blastopore and germ-layer formation

    germ-layers development

  • What is the typical ploidy of most animals?

    Diploid

    ploidy animals

  • What is the usual mode of reproduction in most animals?

    Sexual reproduction

    reproduction animals

  • What type of meiosis do animals exhibit?

    Gametic meiosis

    meiosis animals

  • When do most animals develop tissues?

    During embryogenesis

    development embryogenesis

  • Name the three primary germ layers that form during gastrulation.

    • Ectoderm
    • Endoderm
    • Mesoderm
    germlayers gastrulation

  • What two structures are labeled in the gastrula diagram that relate to the forming gut and its opening?

    • Archenteron (primitive gut)
    • Blastopore

    Gastrulation diagram

    gastrula embryology diagram
학습 노트

Overview

  • The basic animal life cycle: adults (usually diploid) produce haploid gametes by gametic meiosis; gametes fuse at fertilization to form a diploid zygote that undergoes cleavage and embryogenesis.
  • Most animals are diploid (\(2n\)) as adults and have a diplontic life cycle (gametic meiosis).

Key terms & definitions

  • Diploid (\(2n\)): two sets of chromosomes (typical adult condition).
  • Haploid (\(n\)): one set of chromosomes (gametes).
  • Gametic meiosis: meiosis produces gametes; only gametes are haploid.
  • Fertilization: fusion of two gametes: \(n + n = 2n\).
  • Cleavage: rapid, repeated cell divisions of the zygote without overall growth, producing the multicellular embryo.
  • Blastula: a hollow ball of cells with a fluid-filled cavity called the blastocoel.
  • Gastrulation: cell movements that form germ layers and create the primitive gut (the archenteron) and the blastopore.

Stepwise life-cycle & early development

  1. Adult (somatic) stage: usually diploid (\(2n\)). Somatic cells are produced by mitosis.
  2. Meiosis (gametogenesis): germ cells undergo meiosis to make haploid gametes (\(n\)).
  3. Fertilization: sperm and egg fuse to form a diploid zygote (\(2n\)).
  4. Cleavage:
  5. Rapid mitotic divisions without cell growth.
  6. Typical stages: 2-cell, 4-cell, 8-cell.
  7. Cleavage partitions the zygote cytoplasm into many blastomeres.

Basic animal life cycle diagram Alt: Life cycle from meiosis to zygote formation.

  1. Blastula formation:
  2. Continued cleavage produces a blastula: a hollow sphere of cells surrounding the blastocoel.

Cleavage to blastula Alt: Eight-cell stage to blastula (hollow ball with blastocoel).

  1. Gastrulation:
  2. Cells move inward to form the archenteron (primitive gut) and establish germ layers.
  3. The opening formed is the blastopore; its fate differs among animal groups (e.g., protostomes vs deuterostomes).

Blastula to early gastrula Alt: Transition from blastula to early gastrula with blastopore.

  1. Later gastrula & germ-layer differentiation:
  2. Three primary germ layers form in many animals:
    • Ectoderm: epidermis, nervous system.
    • Endoderm: lining of gut and associated organs (e.g., liver, lungs).
    • Mesoderm (when present): muscles, skeleton, circulatory system.
  3. The archenteron becomes the gut; germ layers give rise to tissues and organs during organogenesis.

Later gastrula with germ layers Alt: Later gastrula showing ectoderm, endoderm, and mesoderm.

Important relationships & comparisons

  • Life-cycle ploidy: somatic cells \(=2n\), gametes \(=n\); fertilization restores \(2n\).
  • Gametic meiosis (diplontic) is the dominant pattern in animals; contrasts with haplontic or alternation of generations in other kingdoms.
  • Gastrulation is a major developmental milestone because it establishes body plan layers and axes.

Quick study tips

  • Memorize the sequence: meiosis → fertilization → cleavage → blastula → gastrulation → organogenesis.
  • Be able to label diagrams: blastocoel, blastopore, archenteron, and the three germ layers.
  • Remember typical derivatives of each germ layer (ectoderm: nervous/skin; mesoderm: muscles/blood; endoderm: gut lining).

One-line summary

  • Early animal development converts a single diploid zygote into a multicellular embryo through cleavage, blastula formation, and gastrulation, setting up germ layers and the body plan.