Growth and Development (charlotte) Flashcards
(45 cards)
what is allometry?
how body processes change with body size?
describe surface area and volume ratio in animals.
assuming
what is hypertrophy?
when individuals cells grow larger in size.
what is hyperplasia?
individual cells divide and grow in number.
why do larger animals have more cells?
allows increase in overall size.
different cell types can have specialised functions.
describe adult stem cells
multipotent.
narrower, lineage-restricted.
haematopoietic cells from bone marrow can differentiate into various immune and blood cells.
describe embryonic stem cells
totipotent/ pluripotent.
can differentiate into any cell line.
how is the fertilised egg a source of all differentiate cell types?
all cells have the same DNA.
the process of differentiation allows a specific subset of DNA genes to be expressed = phenotype.
what is metamorphosis?
the ability of larvae to change size and shape. not just growth but also development.
critical in insect evolution as different stages exploit different food resources and habitat so adults and juveniles are not in direct competition with each other.
what is incomplete metamorphosis?
performed by hemimetabolous insects (dragonflies, grasshoppers)
immature = nymphs. several instar stages.
nymphs are similar to adults but lack reproductive organs and often wings.
need to moult their hard exoskeleton between stages to grow in size.
describe parabiosis in kissing bugs
the moult after a blood meal.
decapitated and connected fed and unfed bugs with glass tube - parabiosis.
determined moulting factor was made in brain and travelled in haemolymph.
juvenile hormone = prevents moult.
ecdysteroids = promotes moult.
what is complete metamorphosis?
performed by holometabolous insects. (bees, butterflies).
larvae morphologically different to adult.
imaginal discs - specialised group of cells to form legs, antennae…
larvae eat voraciously and grow then form an inactive pupa or chrysalis.
describe the hormonal control of insect development
brain produced juvenile hormone:
moulting is prevented.
body gets bigger.
brain produces PTTH which simulates a pulse of ecdysone which kickstarts ecdysone elsewhere initiating moulting/ metamorphosis.
what hormone induces moult?
ecdysteroids.
describe steroid hormone action
inactive receptor bound to hsp complex.
steroid crosses membrane and binds to receptor - conformational change.
ligand -receptor dissociates from hsp complex.
two receptors dimerize and bind to hormone response element and active/ repress transcription of target gene.
why is ecdysteroid powerful?
mitogen - causes cell replication = growth.
differentiation factor - cause morphogenesis = development/ maturing.
what are the receptor families of ecdysteroid?
ecdyosone receptor (EcR) and ultraspiracle receptor (USP).
many different variants of EcR and USP and different combinations so can bind 100s of different HRE. turn on and off different genes.
how do insects shed a tough skeleton?
the cuticle is composed of chitin (tough polymer of glucose units).
moulting fluid is induced by ecdysone (chitinase - dissolves chitin).
old endocuticle dissolved and new endocuticle cuticulin basement formed.
apolysis.
ecdysis.
what is apolysis?
digesting old cuticle and making new cuticle.
what is ecdysis?
shedding.
how insects shed?
they take a “big breath” and the old cuticle splits and emerges.
how does the new cuticle become a hard exoskeleton?
the hormone buriscon is released and stimulates hardening.
explain how insect endocrinology can be applied as pest control.
the hormone methoprene is applied as pest control to cause insects to stay juvenile and not reproduce.
used for cat fleas, and mealworms.
how do tough bones grow?
bones are dynamic, living tissue with microcirculatory system so throughout lifetime bone continually absorbs and redeposits.
bones grow from growth plates, growth hormones, osteoblasts concentrate and deposit calcium and phosphate onto collagen of cartilage.
