Lesson 5: Birth, Growth, Reproduction

Question 1

what was the major milestone in tetrapod evolution in regards to reproduction

Answer 1

going from non-amniotic eggs (could not retain water like frog eggs) to amniotic eggs (shelled eggs that could live on land)

Question 2

what are animals who lay amniotic eggs called?

Answer 2

amniotes. which were a group of tetrapod that lay eggs equipped with a special water-tight membrane layer called amnion

Question 3

was it possible to lay huge eggs bigger than half a meter? why or why not?

Answer 3

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

Question 4

definition of histology

Answer 4

the study of bone microstructure as it relates to bone growth

Question 5

cube-square law

Answer 5

as any shaped increases in size, its surface area increases more slowly than its volume

Question 6

osteons

Answer 6

bone cells. as dinos grow, osteons are added to their bones’ outer walls

Question 7

osteocyte

Answer 7

bone cells, formed by bone-creating cells (osteoblasts) becoming surrounded and trapped by the product they secreted

Question 8

what does LAGs stand for and what does it mean

Answer 8

“lines of arrested growth” where rings are created inside dinosaur bones usually during the winter or dry seasons

Question 9

why is LAGs important

Answer 9

help us determine how long it took a dinosaur to grow to a particular size and at what speed

Question 10

what does high vascularity mean and when is it usually present in an organism

Answer 10

Lots of spaces in bone tissue, due to the presence of blood vessels required for bone formation when the animal was allowed. More evident in the bone tissue of young dinosaurs

Question 11

what are the two types of bones:

Answer 11

lamellar bones and Haversian bone

Question 12

definition of lamellar bone and when was it usually present

Answer 12

striated, regularly structured bone tissue which is more visible in the bones of young dinosaurs

Question 13

definition of Haversian bones and when was it usually present

Answer 13

bone tissue that has been secondarily remodeled during the dinosaur’s lifetime (more evident in older dinosaurs)

Question 14

remodeling definition and at what age did it usually occur

Answer 14

occurred in mature dinos. where old bone cells replaced by newer ones

Question 15

what is a series of LAGs known as

Answer 15

known as external fundamental system (EFS). this indicated that the dinosaur is skeletally mature and has stopped growing

Question 16

ontogenetic changes

Answer 16

anatomical changes in an organism that occur as it matures

Question 17

non-isometric ontogenetic changes

Answer 17

changes in the relative proportions of an animal as it grows, that are not simply changes resulting from a general increase in size. e.g. fast growth of the horns and frills of ceratopsians

Question 18

isometric ontogenetic changes

Answer 18

changes in absolute size but not proportions

Question 19

sexual dimorphism

Answer 19

features of the skeleton between males and females that are usually subtle in difference but can be extreme

Question 20

medullary bone

Answer 20

contains concentrations of calcium in females because they lose a lot of calcium when giving birth. only occurs when a female is pregnant

Question 21

predator satiation

Answer 21

reproductive strategy where sauropods produce many offspring’s and provided little to no parental care so that predators would not have been able to eat them all before they matured

Question 22

external fundamental system

Answer 22

a closely spaced series of LAGs, towards the outside of a bone section, formed as growth slows and, eventually, stops

Question 23

what are marrow cavities

Answer 23

spaces inside bone

Question 24

what are oviducts

Answer 24

where eggs come out of. Dinosaurs have 2 functional oviducts and so they lay two eggs at a time

Question 25

As any baby Triceratops grew up, its horns became longer relative to the other proportions of its body. This is an example of what biological phenomenon?

Answer 25

Ontogenetic change

Question 26

Which of the following has not been used to try and identify the sex of a dinosaur specimen?

Answer 26

Lines of arrested growth

Question 27

Which of the following has been used to try and identify the sex of dinosaur specimen

Answer 27

Medullary bone. Eggs within the body cavity. Ornate display structures

Question 28

Which of the following is not an advantage of laying eggs with hard shells? Pick the best possible answer

Answer 28

Improved oxygen exchange rates

Question 29

Which of the following modern animal groups show little or no parental care?

Answer 29

sea turtles

Question 30

What is thought to cause lines of arrested growth?

Answer 30

Seasonal reduction in food availability