Lesson 5: Birth, Growth, Reproduction Flashcards
what was the major milestone in tetrapod evolution in regards to reproduction
going from non-amniotic eggs (could not retain water like frog eggs) to amniotic eggs (shelled eggs that could live on land)
what are animals who lay amniotic eggs called?
amniotes. which were a group of tetrapod that lay eggs equipped with a special water-tight membrane layer called amnion
was it possible to lay huge eggs bigger than half a meter? why or why not?
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
definition of histology
the study of bone microstructure as it relates to bone growth
cube-square law
as any shaped increases in size, its surface area increases more slowly than its volume
osteons
bone cells. as dinos grow, osteons are added to their bones’ outer walls
osteocyte
bone cells, formed by bone-creating cells (osteoblasts) becoming surrounded and trapped by the product they secreted
what does LAGs stand for and what does it mean
“lines of arrested growth” where rings are created inside dinosaur bones usually during the winter or dry seasons
why is LAGs important
help us determine how long it took a dinosaur to grow to a particular size and at what speed
what does high vascularity mean and when is it usually present in an organism
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
what are the two types of bones:
lamellar bones and Haversian bone
definition of lamellar bone and when was it usually present
striated, regularly structured bone tissue which is more visible in the bones of young dinosaurs
definition of Haversian bones and when was it usually present
bone tissue that has been secondarily remodeled during the dinosaur’s lifetime (more evident in older dinosaurs)
remodeling definition and at what age did it usually occur
occurred in mature dinos. where old bone cells replaced by newer ones
what is a series of LAGs known as
known as external fundamental system (EFS). this indicated that the dinosaur is skeletally mature and has stopped growing
ontogenetic changes
anatomical changes in an organism that occur as it matures
non-isometric ontogenetic changes
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
isometric ontogenetic changes
changes in absolute size but not proportions
sexual dimorphism
features of the skeleton between males and females that are usually subtle in difference but can be extreme
medullary bone
contains concentrations of calcium in females because they lose a lot of calcium when giving birth. only occurs when a female is pregnant
predator satiation
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
external fundamental system
a closely spaced series of LAGs, towards the outside of a bone section, formed as growth slows and, eventually, stops
what are marrow cavities
spaces inside bone
what are oviducts
where eggs come out of. Dinosaurs have 2 functional oviducts and so they lay two eggs at a time
