Topic 12-13:Animals Flashcards
animals cell structure and specialization (its unique features)
animals are multicellular eukaryotes
-they lack a cell wall (unlike plants and fungi)
-their bodies are held together by an extracellular matrix called collagen (a protein molecule)
-nervous tissue and muscle tissue are unique, defining characteristic of animals (it gives them the ability to move)
tissues
are a group of cells that have a common structure, function or both
-true tissue is separated by a membranous layer
animals way of obtaining nutrients
they are chemoeteroptohic : they can’t make own carbon-based food sources, they consumer other organism
Hox genes
they control anterior(front, or closest to head) to posterior(back side) developmental sequenced of embryo (pattern formation during development)
-the order of Hox genes along chromosomes similar among different groups of animals
-but the number of repetitions can differ
Homeobox genes and Hox genes-gene regulation
Homeobox genes are a group of genes that encode for transcription factors that regulate the anatomical( cells, tissue and organs )development of organisms- they Regulate morphogenesis
Hox genes are a subset of homeobox genes that specifically, regulate the development of body axes and structures during embryonic development, their function is to Regulate body segmentation and development of appendages(legs, arm, the parts that are attached to the main body)
reproduction and embryonic development
-most animals share a similar pattern of early embryonic development
-have haploid games of different sizes (small motile sperm and large non-motile egg)
-the diploid zygote undergoes a number of mitotic cell divisions (cleavage)
-the cleavage leads to the formation of a multicellular, callow blastula
-the blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissue
embryonic development: first invagination and seconde (the action or process of being turned itself to folded back on itself)
protostomia: first invagination gastrula (blastopore ) becomes the mouth
deuterostomes: the second invagination becomes the mouth (first opening becomes the anus, or closes up )
animal devloepment is…
directional devleopment )embyro contiues gradually on twowards adult form
germ layers
endo -digestive tract (gut)
ecto -> outer covering (skin, nerves)
meso->muscle and other organs
difference between diploblastic and triploblastic
diploblastic endo and ectoderm
triploblastic -endo, ecto and mesoderm
body plans : the two symmetries
-radial symmetry is: no front or back or left or right (they are often sessile (fixed in one place ) or platonic (floats or weak swimmer )
-bilateral symmetry : tow sided symmetry (often move actively and have a central nervous system )
bilateral symmetric animals have…
-a right and left side
- a dorsal (top ) side and a ventral (bottom side )
-an anterior (head) and posterior (tail ) ends
cephalization is
the development of a head
association between body symmetry and the nervous system
-radical symmetry =nerve network
-bilateral symmetry=central nervous system
bilateral symmetry and cephalization
-concentration of sensory organs in the head (brain)
-adapted for forward and directional movement
-quicker reasons to stimuli in the environment
-better able to search for food
-better defense capabilities
coelom
most triploblastic animals possess a fluid-filled body cavity, it’s deprived of mesoderm
-it cushions internal organs from blow to outside body
-allow internal organs to shift within deforming outside of body
-fluid filled cavity can be used as a hydrostatic skeleton
pseudocoelomate
animals lack complete mesodermal lining
the key shared derived characteristics of animals
-multicellularity -collagen
-Diploblastic Hox genes Tissues
-Bilateral symmetry
-Triploblastic
-Cephalization
the common ancestor of animals is a ….
heterotrophic protist
animals common ancestor resembles what…
Choanoflagellates
-which are heterotrophic protists
-single flagellum surrounded by collar of microvilli (fingerlike
projections of cell membrane)
-cell morphology very similar to that of sponges (Porifera)
Evolution of Multicellularity
ball-shaped colony of choanoflagellates may
have evolved into a simple animals with endo- and ectodermal
layers
If cooperative aggregations of cells are able to survive better and produce
more offspring than their unicellular counterparts (higher relative
fitness), then these various evolutionary pathways could all be possible.
the advantage of muticcllularity
-coordination among cells
-specialized cells for different functions
– protective skin
– enzyme secretion for trapping food
– coordinated movement
(or movement of water across food traps)
– specialized cells for reproduction
Palaeozoic Era
Cambrian explosion : marks
the earliest fossil appearance
of many major groups of living
animals
* Suddenly complex life -
including many forms with
skeletons
* Most major phyla appeared
why is animal diversification so late
- [O2] in oceans and
atmosphere was low
until Cambrian
-need O2 to support the metabolism of large, active animals
