Birth, Growth and Reproduction Flashcards
what is the term given to the idea that male and female of the same species are actually different
sexual dimorphism
it is common for _____ features to be ontogenetic changes
sexual dimorphic
Amniotic eggs are:
a) watertight
b) airtight
c) both
d) neither
a) watertight
What is the name given to animals that lay amniotic eggs?
amniotes
what two dinosaurs did palaeontologists suggest were sexually dimorphic
ceratopsian protoceratops and the ancient bird, confuciusornis
What is the evolutionary significance of the amniotic egg?
watertight –> retain water and can be laid in dry habitats –> allow amniotes to colonize terrestrial environments
Describe the shell of the an amniotic egg.
- tough, leathery, hard
- has tiny holes
Why do amniotic eggs have tiny holes?
allow gas exchange
How big is the largest known dinosaur egg? What law explains why there is a limit on how large a dinosaur egg can be?
- largest egg is half a meter long
- cube-square law: amount of oxygen that a dinosaur in an egg requires is a function of its volume
What are bone cells called?
osteons
TRUE of FALSE: as dinosaurs grow, they add osteons to their bones
TRUE
What does LAG stand for? What can they be used to determine? What are LAGs analogous to?
- LAGs - lines of arrested growth (seen as rings in a bone cross-section)
- determines how long it took a dinosaur to grow to a particular size and at what speed it grew
- analogous to rings of a tree trunk
what are some ways to determine if the dinosaur was a female or male
- if the skeleton was found with eggs preserved inside its body cavity - it is a female (other reasons do have to be ruled out, such as eating the eggs before they died)
- if the dinosaur has grown a medullary bone
how does the medullary bone tell us that the dinosaur is a female
in order to lay eggs, the female needs to provide a lot of calcium and the medullary bone contains a large concentration of calcium. the medullary bone acts as a storage prior to the development of the eggs
why is the evidence of medullary bone and association with females limited
medullary bone is only grown prior to egg production and not at other times. so if we find a skeleton with medullary bone we cannot assume it is male because it may have been a female that was not ready to lay eggs
what are two living relatives of dinosaurs
crocodiles and modern birds
true or false - skeletons of young dinosaurs are never found alongside the adult dinosaurs
false - they are
what species is the largest of all dinosaurs
sauropods
true or false - mother sauropods are able to lay large eggs
false - instead they are able to lay many eggs
what kind of strategy did sauropods use in terms of their eggs
predator satiation - they produced so many offspring at one time so that the predators could not have been able to eat them all while young
in order to produce a new generation of sauropods….
only a small amount of the eggs laid needed to hatch and mature
what other modern animal uses the predator satiation
sea turtles
why are female crocodiles good parents
they guard their nests and protect their children for a long period of time after hatching
what are examples of amniotes
mammals, birds, dinos and reptiles
true or false - growth slows down during winter
true
what dinosaur took only 20 years to grow to its adult size
T rex
what are two features of bones in younger dinos
high vascularity - many blood vessels
lamellar bone - collagen
true or false - younger bones undergo remodeling
false - mature bones do
after remodeling, the new bone is called ____ or _____
Haversian or secondary bone
what does an external fundamental system tell us
the skeleton of a dinosaur is fully mature and has stopped growing
what does the external fundamental system contain
spaced series of lines of arrested growth
define ontogenetic changes
changes of an organism as the dinosaur matures
given two examples of ontogenetic changes mentioned in the lecture
crests of hadrosaurs formed as they matured
no armour or tail cubs in ankylosaurs until they mature
explain the important features of Baby
it is a Chasmosaurus and they provide an example of non-isometric changes
-> the frill on the adult is proportionally longer than the younger one
-> the frill develops at a faster rate than any other part of the skull
Baby also provides an example of ontogenetic changes
-> nasal horn only develops as they mature
what is an example of a non-isometric change in T rex
in young dinosaurs, tibia is longer than femur
-> in adults the tibia and femur are the same length
________ are changes in absolute size but not proportions
isometric ontogenetic changes
provide an example of isometric ontogenetic change
ceratopsian hind legs changed proportionally as it grew
what are marrow cavities
they are spaces for medullary bone to grow
true or false - eggs are all the same shapes and sizes
false
