Chapter 5 Flashcards

1
Q

What are the characteristics of amniotic eggs

A
  • they have encapsulating membranes that are watertight
  • > note animals that lay amniotic eggs are called amniote
  • being able to hold in their own water
  • > amniotic eggs can be held in dry environments
  • > note shells improved amniotic eggs to hold in more water and made the eggs more durable and less vulnerable to small predators
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2
Q

Are mammals, birds, dinosaurs and reptiles all amniotes?

A

-yes they are all amniotes

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3
Q

Are amniotic eggs airtight

A
  • no they are just water tight

- >other wise the eggs would suffocate

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4
Q

Were large dinosaur eggs possible

A
  • no
  • > because the amount of oxygen that a dinosaur developing inside an egg requires is a function of its volume
  • > while the rate at which oxygen can be exchanged is a function of the eggshell’s surface area

-giant eggs would have a low ratio of surface area to volume and would die

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5
Q

What are lines of arrested growth

A
  • the rate at which osteons are added to bones is not the same
  • > during times when resources are scarce, growth may slow down
  • > this creates rings inside the bones

-these rings are referred to as lines of arrested growth

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6
Q

How do lines of arrested growth help paleontologists

A
  • they can be studied in old and young dinosaurs

- >and used to determine how long it took a dinosaur to grow to a particular size and at what speed the dinosaur grew

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7
Q

What are the bones of younger dinosaurs characterized by

A
  • they are characterized by high vascularity and a texture called lamellar bone
  • > note for younger dinosaurs, lines of arrested growth grow later as they grow
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8
Q

What do more mature dinosaurs go through in terms of their bone processes

A
  • they go through a process called remodeling
  • > essentially where the old bone cells were replaced by newer bone cells
  • > these newer bone cells are called Haversian or secondary bone cells
  • as growth slows and then stops
  • > a closely spaced series of lines of arrested growths form
  • > these are referred to as the external fundamental system(EFS for short)
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9
Q

What does the EFS indicate

A

-that the dinosaur is skeletally mature and has stopped growing

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10
Q

What are ontogenic changes

A
  • changes in the form of an organism that occur as it matures are called ontogenic changes
  • > some ontogenic changes involve the growth of entirely new structures
  • note big heads and big eyes are common traits of young animals
  • > baby dinosaurs also had relatively large heads and eyes
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11
Q

What are non-isometric ontogenic changes

A
  • not simply changes resulting from a general increase in size
  • > certain features appear at different rates in an organisms life or do not grow proprotionally with the rest of the body
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12
Q

What are isometric ontogenetic changes

A
  • changes in absolute size but not proportions
  • > for example, the length of the tibiaa relative to the length of the femur of a baby ceratopsian was nearly the same as the length of the tibia relative to the length of the femur of a full-grown adult
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13
Q

What is sexual dimorphism

A
  • the males and females of the same species are different
  • > they are usually subtle but can be extreme

-it is common for sexually dimorphic features to be ontogenic changes as you are not just born with them

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14
Q

What is a medullary bone

A
  • laying eggs with hard shells require a female to donate a large quantity of calcium
  • > in preparation for this, the female grows a medullary bone

-medullary bone contains concentrations of calcium that are stored prior to eggshell development

  • this bone can be used to identify certain dinosaur genders of a specific species
  • > however, females without medullary bones could mean that they were not getting ready to lay eggs
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15
Q

What is predator satiation

A
  • to produce a new generation, only a tiny fraction of eggs that were laid needed ot hatch and grow into adults
  • > rather than investing time into guarding and rearing young, some dinosaurs like the sauropods did this
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