96 terms

Biology 1108 Lecture Exam 4


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Cambrian Explosion
-an adaptive radiation event
-rapid diversification of animal body types and lineages
-at the end of the Cambrian Explosion, virtually every major group of animals had appeared.
What triggered the Cambrian Explosion
-higher oxygen levels
-evolution of predation
-new niches beget new niches
-new genes, new bodies
5 shared traits of most animals
1. Multicellular
2. Heterotrophic that ingests food
3. lack cell walls, but have extensive extracellular matrix that lets the cell adhere and communicate
4. most animals arranged in tissue
5. sexual reproduction with similar early embryonic development (blastula & gastrula)
Early Embryonic Development
After fertilization and formation of a diploid zygote, zygote undergoes cleavage to form a blastula.
rapid series of mitotic divisions with no cell growth in between
hollow ball of cells that migrate inwards
Archenteron (pouch to become digestive tract)
Closest living relative to animals
Four aspects of the animal body plan
1. Evolution of Body Symmetry
2. Origin and elaboration of tissues
3. Evolution of a fluid filled body cavity
4. Variation in events of early embryonic development
3 types of body symmetry
1. Asymmetry
2. Radial Symmetry
3. Bilateral Symmetry
Nervous Systems associated with body symmetry
Asymmetrical: lack nerve cells
Radial Symmetry: have a nerve net
Bilateral Symmetry: central nervous system (CNS)
formation of head region where sensory organs are concentrated
2 tissue layers
3 tissue layers
Animals with true tissues
enclosed fluid-filled cavity (triploblastic and bilateral only) Provides movement, space, storage and a container for organs
flatworms - no coelom
a pseudocoelom (literally "false cavity"), which is a fluid filled body cavity. Tissue derived from mesoderm only partly lines the fluid filled body cavity of these animals. Thus, although organs are held in place loosely, they are not as well organized as in a coelomate.
Bilateral triploblastic animals can be split into 2 groups
Protostome and Deuterostome
-spiral cleavage
-determinate cleavage
-coelom forms as splits into mesoderm
-first opening is mouth from blastopore
-mouth on bottom
-radial cleavage
-interdeterminate cleavage
-coelom forms as mesoderm buds from the walls of the archenteron
-blastopore becomes to anus
tube-within-a-tube design
99% of animals are bilaterally symmetrical and triploblasts with coeloms and protostome or deuterostome development
5 key points about animal phylogeny
1. All animals share a common ancestor
2 Sponges are the basal taxon
3. Eumetazoa is a clad of animals with true tissues
4. Most animals belong to the clade Bilatera
5. There are 3 major clades of the bilateral animals.
Role of innovative methods to diversification of animals
-sensing the environment
Sensory Organs
Concentration of sensory organs in the head region is a key aspect of cephalization
Variety of Sensory abilities
-Magnetism: sense magnetic fields
-Electric Fields: sense disruptions in electrical field
-Barometric pressure: detect severe drop in BP
4 feeding strategies of animals
1. Filter feeders
2. Deposit feeders
3. Fluid feeders
4. mass feeders
filter feeders
suspension feeders
-variety of mouth parts and structures bring in water & trap debris & bring water
Deposit feeders
take in substrate (soil) and digests out organic and nutrients and takes the rest out
Fluid Feeders
animals that eat fluids
Mass feeders
take chunks of food in mouth
-bite and chew
Four functions of animals locomotion
-finding food
-finding mates
-escaping from predators
-dispersing to new habitats
Evolution of the limb
The evolution of the limb made highly controlled and rapid movements possible
unjointed limbs
lobe like limbs
Jointed limbs
make fast, precise movements possible
("live bearing") mammals
"egg bearing"
egg-live bearing
-embryos develop in egg, and mother not sharing nutrition, eggs hatch in mother
change from immature body form to an adult body form
3 stages of metamorphosis
forms the gastrula
the opening of the central cavity of an embryo in the early stage of development.
Why are Invertebrates a paraphyletic group?
95% of animal species
-occupy almost every habitat
-immerse diversity of forms & sizes
-not all animals are invertebrates.
Porifera Sponges
-5500 species
-found in benthic marine habitats
-asymmetrical with no tissues
-filter feeders-choanocytes
-10000 species
-found in marine habitats from planktonic to benthic
-both sessile & motile species
(medusa & polyp)
-radial symmetry diploblasts with a nerve net
-8 phyla-grow continuously & incrementally
-most have digestive tract with two openings and a coelom
-some have a lophophore and trochophore(these are not derived traits)
8 phyla of Lophotrochozoans
Segmented body of Annelida
evolved multiple times
function in suspension feeding in adults
larvae swim & may feed
-8 phyla
-thick cuticle or hard exoskeleton
-grow by molting (shed)
-includes most successful group of animals (arthropods)
-Deuterostome development
-includes invertebrates & some vertebrates
7000 species
-exclusively marine
-bilaterally symmetrical larvae, pentaradial symmetrical in adults
-Endoskeleton composed of calcium carbonate
-water vascular system: uses water pressure to direct movement
4 shared derived traits of members of Chordata
All chordates have:
-Hollow Nerve Cord
-Pharyngeal slits
-Muscular post anal tail
3 groups of Chordates
1. Cephalochordata
2. Urochordata
3. Vertebrates
-has all 4 features in larvae form & adult
-filter feeders
-all 4 features in larvae, in adult only gill slits remain
-has all 4 features in larvae, in adults the notochord develops into backbone, nerve cord develops into spinal cord
-the gill slits in aquatic vertebrae develop into gill slits turn into ears, some lose post anal tail
2 derived traits of vertebrates
-vertebrae and cranium
Vertebrae fossil record
- vertebrae first appear in the fossil record during cambrian explosion
-earliest members had streamlined, fishlike bodies and a cartilaginous skull
-series of key adaptations in vertebrate evolutionary history
shared derived traits of Gnathostomes
-paired fins
Shared derived traits of Osteichythyans
-bony endoskeleton
Shared derived traits of tetrapods
-limbs w digits
-true lungs
Hypothesized origin of Vertebrae Jaw
-origin hypothesized to be from mutations that affected the morphology of gill arches
Evidence of hypothesis of vertebrae jaw
1. both consists of flattened bony or cartilaginous bars that hinge or bend forward
2. The same cell population develops into muscles for each structure
3. Both are derived from specialized embryonic cells called neural crest cells
evolutionary importance of lobe finned fish
represent a crucial link between fish and tetrapods
evolution of the tetrapod limb
-gradual transition from lobe-like fin to a limb that could support walking on land
-supported by fossil & molecular evidence
-lungs for gas exchange
Structure of the amniotic egg and its importance
allowed embryo development to occur in dry conditions
-series of specialized membranes, developed from tissue layers
-Chorion- outer/gas exchange
-Allantois- gas exchange/waste disposal
-Amnion- shock absorber
-Yolk- nutrition provider
external shell covering to reduce desiccation
What trait do birds and mammals share?
They are both endothermic. (maintain constant body temperature) and this evolved twice in birds and mammals
Hypothesis on why feathers evolved
-feathers evolved in dinosaurs
three adaptations in birds that increased flight efficiency
-elongated keel on sternum provided high surface area for flight muscle attachment
-reduced # of bones & organs (hollow bones)
-ability to maintain body temperatures (endothermic)
Parental Care
fitness tradeoff for mother
-anything a parent does to ensure survival of offspring
rich in blood vessels and facilitates a flow of oxygen and nutrients from mother to developing offspring
Advantages of Placenta
1. Offspring develop at constant, favorable temperature
2. Offspring are protected
3. Offspring are portable
a cartilaginous skeletal rod supporting the body in all embryonic and some adult chordate animals.
hollow nerve cord
develops into nervous tissue of the brain and spinal cord
Pharyngeal slits
Pharyngeal slits are filter-feeding organs found in Invertebrate chordates (lancelets and tunicates) and hemichordates living in aquatic environments.
post anal tail
A post-anal tail is an extension of the body that runs past the anal opening. In some species, like humans, this feature is only present during the embryonic stage.
presence of hair or fur
-mammary glands
-differentiated teeth
3 groups of mammals
1. Monotremes: lay eggs
2. Marsupials: pouched animals
3. Eutherians: placental animals
3 levels of biodiversity
1. Genetic Diversity
2. Species Diversity
3. Ecosystem Diversity
sense of connection to nature and all life
benefits of biodiversity
-Ecosystem services: functions performed by an ecosystem that directly or indirectly benefits humans
Endangered species
at risk of going extinct
Threatened species
numbers declining, approaching endangered
The threats to biodiversity
-habitat loss
-invasive species
-global change
Habitat Loss
single greatest threat to biodiversity throughout the biosphere
-includes habitat destruction, fragmentation and degradation
Introduced Species
species that have moved from native locations to new geographic regions
Invasive Species
non-native species that cause damage
excess nutrient enrichment to water
-caused by excessive fertilizers, agricultural wastes, sewage, outflow and deforestation
-critical load of ecosystem exceeded
ex. Gulf of Mexico
Conservation Biology
integration of several fields with in the aim of diversity
Global Climate Change
-Link between increased concentration of atmosphere CO2 & increased global temperature.
Greenhouse Effect
-atmospheric accumulation of CO2 & other gases absorb reflected infrared radiation & reradiate some back to Earth
2 types of Greenhouse Effects
1. Natural Greenhouse Effect
2. Human Enhanced Greenhouse effect
Phylogenetic Tree of Animals