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animals > lecture 2 - 01/10/24 > Flashcards

lecture 2 - 01/10/24 Flashcards

1
Q

What is fertilisation?

A

Fusion of sperm and egg

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2
Q

What is cleavage?

A

mitotic cell division after fertilisation
- no time for cells to increase in size

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3
Q

What are the 2 types of cleavage?

A

spiral and radial

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4
Q

Describe spiral cleavage

A

seen in protostomes animals
cell pattern rotates by 45 degrees
e.g. pond snail

O O OQO
—–> Q Q
O O OQO
4-cell stage 8-cell stage

O = 1st cells
Q = replicated cells

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5
Q

Describe radial cleavage

A

seen in deuterostomes animals
cells stack in an aligned manner
e.g. sea urchin

O O Q Q
—–>
O O Q Q
4-cell stage 8-cell stage

O = 1st cells
Q = replicated cells

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6
Q

Describe the blastula stage

A
  • dividing cells are aligned in the outer layer
  • inside of the embryos forms a cavity called
    ‘blastocoel’
  • cells in blastula stage are not easily
    differentiated
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7
Q

What does the blastocoel contain?

A

salt water

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8
Q

What are the 3 germ layers?

A

ectoderm
mesoderm
endoderm

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9
Q

What is a germ layer?

A
  • a group of cells which are specified to
    become certain cell fates
  • formed at the late blastula stage
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10
Q

What does the ectoderm form in humans?

A

neutral plate
- forebrain
- midbrain
- hindbrain
- spinal cord

neutral crest

placodes
- eyes
- nose
- ear

epidermis (skin)

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11
Q

What does the mesoderm form in humans?

A

muscle
bone
kidney
heart
blood

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12
Q

What does the endoderm form in humans?

A

intestine
pharynx
liver
stomach

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13
Q

Describe the trend between complexity and number of germ layers

A

As number of germ layers increases, complexity increases

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14
Q

What is the term for 2 germ layers?

A

diploblastic

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15
Q

What is the term for 3 germ layers?

A

triploblastic

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16
Q

What does evolution of germ layers allows?

A

it allows the development of different tissues with complex functions

17
Q

How many germ layers does porifera have?

A

no germ layers

18
Q

How many germ layers does Ctenophora and Cnidaria have?

A

2
diploblastic

19
Q

How many germ layers do the Bilateria have?

A

3
triploblastic

20
Q

Describe Gastrulation

A

rearrangement of cells
- involution and internalisation of mesoderm
and endoderm cells

specification of cell fates
- ectoderm > epidermis, neuron
- mesoderm > muscle, blood etc.
- endoderm > digestive system

21
Q

What is radial symmetry?

A

one main axis

22
Q

What is bilateral symmetry?

A

Plane of symmetry runs from anterior to posterior.

23
Q

Explain the evolution of symmetrical animals

A

asymmetrical –> radially symmetrical –> bilaterally symmetrical

24
Q

What is the exception that breaks the bilaterally symmetrical rule in the bilateral?

A

echinoderms are bilateria but have lost bilateral symmetry

25
Q

Why is bilateral symmetry important?

A

It facilitated dorsal-ventral differentiation of more complex tissue development

26
Q

What groups are in protostomia?

A

ecdtysozoa
lophotorochozoa

27
Q

What is the difference between cleavage pattern in protostomes and deuterostomes?

A

protostomes = spiral cleavage
deuterostomes = radial cleavage

28
Q

What is the difference between cell fates during cleavage in protostomes and deuterostomes?

A

protostomes = determinate cleavage - tissue e.g. skin, muscle

deuterostomes = indeterminate cleavage - complete larvae

29
Q

Protostomes vs deuterostomes mouth or anus first?

A

protostomes - blastopore forms mouth
deuterostomes - blastopore forms anus

30
Q

Do acoelomates have a body cavity?

A

no body cavity

space between gut and muscular wall filled with masses of cells - mesenchyme

31
Q

Do pseudocoelomates have a body cavity?

A

yes - pseudocoel

muscle (mesoderm derived) present only on outer side of pseudocoel

no mesoderm surrounding internal organs

32
Q

Do coelomates have a body cavity?

A

yes - coelom

internal organs surrounded by muscular tissue - peritoneum

coelom is enclosed both inside and out by mesoderm

33
Q

Explain the evolution and complexity of body cavity

A

acoelomate –> pseudocoelomate –> coelomate

gets more complex –>

34
Q

How do earthworms move?

A

peristalsis

bristles anchor the worm and muscles manipulate the fluid in the coelom flattening and lengthen sections of the animal allowing it to move

35
Q

What is a hydrostatic skeleton?

A

closed body compartment filled with fluid under pressure

36
Q

Are fluids compressible?

A

fluids are relatively uncompressible

37
Q
A

animals (4 decks)

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