Lecture 16: Animals Flashcards
Animal cell structure
- multicellular eukaryotes
- lack cell walls
- bodying cells are held together by proteins like collagen
- nervous tissue and muscle tissue are unique –> ability to move
- tissues are a group of cells that have a common structure, function or both
Characteristics of animals
- chemoheterotrophic: cannot make own carbon based food source and must consume other organisms
- sexual reproduction: motile haploid sperm fertilizes larger non motile haploid egg to make diploid zygote
- capable of movement in at least one stage of life cycle
Reproduction and embryonic development
- haploid gametes of different sizes (small motile sperm, large motile egg)
- diploid zygote undergoes a # of mitotic cell divisions known as cleavage
- cleavage leads to the formation of a multicellular hollow blastula
- the blastula undergoes gastrulation, forming a gastrula w/ different layers of embryonic tissues
2 types of cell cleavage
Protostomes: the new row of cells is twisted slightly off centre
- it’s a spiral cleavage
- determinate: new cell is destined to form some part of the later embryo therefore removal of some cells results in embryo missing organs
Deuterostomes: each cell division stacks the new cells directly above the previous ones
- radial cleavage
- Indeterminate: early embryonic cells not differentiated (could split young embryo and get two complete later embryos which results in identical twins
2 types of embryonic development
- Protostomia: first invagination of the gastrula (blastopore) becomes the mouth
- Deuterostomia: Second invagination becomes the mouth
2 types of body plans
- Radial symmetry: no front and back or left and right (ex: sea anemones, comb jellies)
- Bilateral symmetry: 2 sided symmetry (right and left) ex: lobster, humans
- a dorsal (top) side and a ventral (bottom) side
- anterior (head) and posterior (tail) ends
- Cephalization is the development of a head
Bilateral symmetry and cephalization
- concentration of sensory organs in head
- adapted for forward and directional movement
- quicker response to stimuli in the environment
- better able to search for food
- better defensive capabilities
what is Eumetazoa?
- Animals with true tissues
- tissue is integrated groups of cells w/ common structure and function, isolated from other tissues by membraneous layers
What are the 3 types of germ layers?
- Endo: digestive tract (gut)
- Ecto: outer covering (skin and nerves)
- Meso: muscle and other organs
what does Radiate and Bilateria refer to?
Radiata is 2 embryonic cell layers
- diploblastic: endo and ectoderm
Bilateria is 3 embryonic cell layers
- triploblastic: endo, eco, and mesoderm
Body cavities have…
- most triploblastic animals possess a fluid filled body cavity
- a true body cavity is called a coelom
- coelomates are animals that posses a true coelom
- hemocoelomate: are animals that lack complete mesodermal lining
- some triploblastic animals have a hemocoelom
triploblastic animals that lack a body cavity are called what?
Acoelomates
What is the function of the Coelom?
- cushions internal organs from blows to outside body
- allows internal organs to grow and shift w/out deforming outside the body
- fluid filler cavity can be used as a hydrostatic skeleton
- gas exchange and waste removal
The common ancestor resembles Choanoflagellates which are…
- heterotrophic protists
- single flagellum surrounded by collar of micivilli
- cell morphology very similar to sponges
what is the Colonial Hypothesis?
A ball shaped colony of choanoflagellates may have evolved into a simple animal with endo and ectodermal layers
