animals Flashcards
What are the 4 characteristics of animals?
Cell structure and Specialization, Nutritional mode, reproduction, development.
How are cells and tissues interconnected in animals?
extracellular, structural proteins
What two tissues are characterisitic of animals?
muscle and nervous
What is the nutritional mode of animals?
phagotrophic chemoheterotrophs
How does sexual reproduction in animals work?
Gametes are rpoduced by meiosis, fuse to form diploid zygot
3 forms of asexual reproduction in animals?
Fragmentation, fission, budding
What is parthenogenesis?
Development of an unfertilized egg cell into an embryo
What are 2 benefits of asexual reproduction?
Rapid population growth in favourable conditions.
Advantageous when opportunities for sexual reproduction are limited.
How does a zygote develop into an embryo? (3 steps)
1) Rapid mitotic divisions called cleavage form an 8-cell embryo
2) More cleavage forms a blastula with a blastocoele
3) Gastrulation forms a gastrula with a ectoderm and endoderm
What is the archenteron?
Pouch formed in the gastrula which opens to the outside via the blastospore.
What are Hox genes and what do they do?
Highly conserved genes that regulate embryonic development by regulating development along the anterior-posterior axis
Direct development vs Indirect development
Direct development is when the animal after birth is a juvenile version of its adult form.
Indirect development is when an animal has a larval stage that is morphologically and behaviourally different from the adult stage.
Are all animals motile?
Yes, at atleast one stage in their life
What are the two kinds of symmetry in animal body plans?
Radial symmetry - usually sessile
Bilateral symmetry - specialized for directional movement
- also have cephalization
What are the 3 embryonic tissue layers and what do they give rise to?
Ectoderm - skin + nervous system
Endoderm - lines developing digestive tube
Mesoderm - muscle tissue
What is the coelom and what does the coelom do?
fluid-filled body cavity where internal organs develop within the mesoderm
- allows organs to shift without deforming body
- cushions internal organs
- hydrostatic skeleton
What is the hemocoel and what does it do?
Forms between the mesoderm and endoderm and arises from the blastoceoel.
- contains hemolymph which is analagous to blood and circulated throughout the body cavity in an open ciruculatory system by the heart
- involved in circulation, nutrient transport, waste removal and may function as a hydrostatic skeleton
What are animals with coeleoms called?
coelomates.
What are the 2 forms of development in bilateral triploblastic animals? (+ features)
Protostome development
- spiral, determinate cleavage
- mouth forms from blastopore
- coelom forms by splitting of solid masses of mesoderm
Deuterostome development
- radial, indeterminate cleavage
- anus forms from blastospore
- coelom forms by outpocketing of mesoderm from archenteron
What are the basal animals?
sponges
What is the clade of animals with true tissues?
Eumetazoa
What are the 3 major clades of bilaterians?
Deuterostomia, Ecdysozoans, Lophotrochozoans
How are choanoflagellates related to animals? (2 items)
1) cell morphology - choanoflagellate cells + collar cells of sponges are the same
- similar cells found in other animals
2) DNA sequence homology
- molecular phylogeny confirms relationship
What are some hypotheses for the Cambrian explosion?
- Evolution of predators and prey led to developpment of more complex body structures
- Neoproterozoic Oxygenation event led to more energetic lifestyles and greater body size
- Evolution of Hox genes facilitated diversification of body forms
