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Zoology 1 > Development 1: Zygote to organism > Flashcards

Development 1: Zygote to organism Flashcards

1
Q

Define development

A

Series of progressive changes in form and function that occurs during an organism’s life cycle

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2
Q

What does development continue until?

A

Death

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3
Q

What are the 5 key stages of development?

A
  1. Fertilisation
  2. Cleavage
  3. Gastrulation
  4. Organogenesis
  5. Morphogenesis
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4
Q

What is fertilisation?

A

1 sperm enters egg.
- inside paternal and materinal genetic material fuse = diploid cell
- stimulates cleavage

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5
Q

Which parent do the cytoplasm and mitochondria of the zygote come from?

A

Mother

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6
Q

Which hemisphere is the nucleus in (in most species)?

A

animal hemisphere

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7
Q

Which hemisphere do nutrients accumulate?

A

Vegetal hemisphere

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8
Q

In what class does the ‘grey crescent’ appear?

A

Amphibians

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9
Q

Describe the grey cresent

A
  • In amphibians sperm enters the animal hemisphere, the cortex rotates exposing the grey crescent
  • Proteins in the grey crescent control what form the cells will take
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10
Q

What is cleavage?

A

Rapid series of cell divisions

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11
Q

What is each cell produced during cleavage called?

A

Blastomere

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12
Q

How many patterns of cleavage are there, and what are they?

A

Complete
Incomplete-discoidal
Incomplete-superficial

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13
Q

What does cleavage pattern depend on?

A

Species dependent:
- Depends on amount of yolk and orientation of spindles

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14
Q

Describe complete cleavage

A

No yolk = all cells are equal size e.g sea urchins
Yolk gets in the way of the cleavage furrow = cells divide asymmetrically e.g frogs

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15
Q

Describe incomplete cleavage - discoidal

A
  • With lots of yolk the cleavage furrows don’t penetrate the yolk = cleavage is incomplete
  • A blastodisc forms on top of the yolk
    E.g birds
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16
Q

Describe incomplete cleavage - superficial

A
  • Nucleus divides but cytokinesis doesn’t occur
  • Nuclei migrate to the edge & membrane grows inward = nuclei partitioned into individual cells
    E.g insects
17
Q

Describe radial cleavage

A

mitotic spindles form at right angles/ parallel to animal- vegetal axis

18
Q

Describe spiral cleavage

A

Mitotic spindles are oblique angles (diagonal) to a a-v axis

19
Q

Describe rotational cleavage

A

first division is parallel to a-v axis, second is at right angles = ‘disorderly’ arrangement of daughter cells

20
Q

Early in development cells can be described as ________

A

totipotent

21
Q

define totipotent

A

any cell can become any cell type

22
Q

What is determination

A

When a cells fate is fixed (fate map)
- cells become structurally and functionally specialised

23
Q

What is gastrulation?

A

process where a blastula is transformed into an embryo with body axes and 3 tissue layers
→ one of the most important stages in development

24
Q

What is the endoderm?

A

Inner layer - gastrointestinal tract, inc. liver, pancreas, and respiratory system

25
Q

What is the mesoderm?

A

middle layer - bone, muscle, heart, kidneys, bladder, ovaries/testes and inner layer of skin

26
Q

What is the ectoderm

A

outer layer of skin and nervous system

27
Q

In birds and reptiles, where does the epiblast originate from?

A

The blastodisc

28
Q

In mammals, , where does the epiblast originate from?

A

The inner cell mass

29
Q

In birds, what are the epiblast and they hypoblast?

A

Epiblast → embryo
Hypoblast → extraembryonic membranes

30
Q

In mammals, what is the yolk replaced by?

A

A placenta

31
Q

What is organogenesis?

A

the formation of organs

32
Q

What is neurulation and when does it occur?

A

Early in organogenesis begins the formation of the nervous system in vertebrates

33
Q

Describe the 3 stages of neurulation

A
  1. Thickening of the ectoderm = neural plate
  2. Edges of neural plate thickens further, creates ridges
  3. Ridges fuse over the top = cylinder (neural tube)
34
Q

Describe body segmentation

A
  • Somites produce the vertebrae, ribs and muscles of the trunk and limbs
  • Neural crest cells produce peripheral nerves
35
Q

What are the 4 extraembryonic membranes in birds?

A

Yolk sac
Amniotic sac
Chorion
Allantois

36
Q

What is the function of the yolk sac in bird eggs?

A

= nutrient transfer (through blood vessels)

37
Q

What is the function of the amniotic sac in bird eggs?

A

= surrounds embryo and secretes fluid = protection

38
Q

What is the function of the chorion in bird eggs?

A

= limits water loss & allows gas exchange

39
Q

What is the function of the allantois in bird eggs?

A

= Sac stores metabolic waste

Zoology 1 (26 decks)

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