Lecture 2- Vertebrate Origins And Evolution Flashcards
What is ontogeny?
> ontogeny refers to the embryonic development of an organism as well as any development changes that occurs after birth or hatching (I.e., reproductive maturation, aging, etc.)
Summarize Von Baer’s Law.
> features that develop earliest in ontogeny are the oldest phylogenetically
features that develop later in ontogeny are more recent phylogenetic developments
features common to all members of a major taxonomic group develop earlier in ontogeny than do special features that distinguish subdivisions of the group
What is teleology?
> the idea that characteristics develop because they are needed
EXAMPLE: birds are needed to fly, so they developed wings
What are the components of the synthetic theory of evolution?
> organic evolution
genetic diversity
theory of natural selection
Summarize organic evolution
> organisms living today are not necessarily the same as those that lived in the past
organisms living in the past are not necessarily the same as those living today
based primarily on fossil record
Summarize genetic diversity
> all members of a population demonstrate genetic variation (identical twins may be an exception)
sources of genetic variability:
» sexual reproduction:
»» meiosis (independent assortment and crossing-over)
»» recombination (fertilization)
» mutation
The theory of natural selection was co-developed independently by whom?
> Charles Darwin
» published “On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life;” 1859
Alfred Russel Wallace
What are the components of the theory of natural selection?
> genetic variability exists in sexually reproducing populations
> some members of the populationn may be better “fit” for a given environment than others
> these individuals have a better chance of survival and of having fertile offspring
> the genotype a of these individuals will become more frequent in a population over many years
> if the environment does not change, then the population may achieve genetic equilibrium, and evolution may take place very slowly or not at all
What theory was developed by Jean Baptistery Lamarck?
> theory of acquired characteristics
The theory of acquired characteristics was developed by who?
> Jean Baptiste Lamarck
What are the components of the theory of acquired characteristics?
> during its lifetime an organism may develop an atomic changes in response to specific pressures it encounters
these acquired characteristics may then be passed on to its offspring
Summarize analogy, a term relating to origins and comparative anatomy.
> similarity in function in structures in two or more different species
> although the function in similar (I.e., wing of bird and wing of insect), neither the anatomy nor the embryological development is similar
> structures that are similar in function but that do not have a similar anatomical structure and/or embryological development are referred to as being analogous (noun = analogue). Organisms possessing these structures do not derive these structures from a common ancestor
Summarize homology, a term relating to origins and comparative anatomy.
> structural similarity uniquely evolved (due to inheritance) from a common ancestor or developed from a common embryonic a late.
> anatomy and development are similar, but function does not have to be similar
> of greater interest in this course are those structures found in different organisms that are similar in their anatomical structure and embryological development and that may or may not be similar in function
> such structures are referred to as homologous (noun= homologous)
> these structures are derived from an ancestor common to all organisms possessing these structures
> an example to be considered later are the set of middle ear bones in the human ear an certain elements of the upper and lower jaws found in fishes
Define homoplasy.
> structural similarity in different organisms not due directly to inheritance from a common ancestor or development from a common embryonic anlage
Define parallelism
> independent development of similar characteristics in lineages that inherit from a common ancestor a potential for such development but do not directly inherit the similar characteristics
Define convergence
> independent development of similar characters in two or more lineages even though they receive from the common ancestor neither the adaptations involved not characteristics that channel the development of those adaptations
Summarize paedomorphosis.
> larval form does not metamorphose > larval form becomes the adult form > larval form develops gonads and becomes sexually active > example: >>> amphioxus
Summarize neoprene
> type of paedomorphosis
adult form retains one or more larval characteristics
example:
» external gills in salamander such as Necturus (
The earth is thought to be over ________ billion years old?
> four
The appearance of vertebrates in the fossil records began almost _________ hundred million years ago?
> five
What are the geological subdivisions of the earth’s history?
> eons
» Precambrian eon (4.5 billion to 570 million years ago)
»» earliest life forms may have originated about 3.2 billion years ago, but there were no vertebrates during this eon
» Phanerozoic eon (began about 570 million years ago)
subdivisions of eons
» eras
» periods
» epochs
What are the subdivisions of eons?
> eras
periods
epochs
The quaternary and tertiary periods occurred during what era of the Phanerozoic eon?
> Cenozoic era (65 million years in duration)
The Cretaceous, Jurassic, and Triassic periods occurred during what era of the Phanerozoic eon?
> Mesozoic eon (165 million years in duration)
The Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian periods occurred during what era of the Phanerozoic eon?
> Paleozoic era (340 million years in duration)
Name the period and era of the Phanerozoic eon that the Holocene and Pleistocene epochs belong to
> quaternary (period)
> Cenozoic (era)
Name the period and era of the Phanerozoic eon that the pliocene, Miocene, Oligocene, Eocene, and Paleocene epochs belong to
> tertiary (period)
> Cenozoic (era)
What major event occurred during the Cambrian period of the Paleozoic era of the Phanerozoic eon?
> first appearance of vertebrates in the form of armored ostracoderms
What major event occurred during the ordovician period of the Paleozoic era of the Phanerozoic eon?
> ostracoderms only vertebrates, but armor disappearing; fishes became more active swimmers
What major event occurred during the Silurian period of the Paleozoic era of the Phanerozoic eon?
> appearance of primitive jawed fishes
What major event occurred during the Devonian period of the Paleozoic era of the Phanerozoic eon?
> fishes were the dominant vertebrates but amphibians began to appear
What major event occurred during the Carboniferous period of the Paleozoic era of the Phanerozoic eon?
> amphibians are abundant and reptiles began to appear
What major event occurred during the Permian period of the Paleozoic era of the Phanerozoic eon?
> reptiles became the dominant vertebrates
What major event occurred during the Triassic period of the Mesozoic era of the Phanerozoic eon?
> first dinosaurs appeared along with turtles and marine reptiles
What major event occurred during the jurassic period of the Mesozoic era of the Phanerozoic eon?
> reptiles dominant
What major event occurred during the cenozoic era of the Phanerozoic eon?
> all modern families and most modern genera of mammals present by end of era
What major event occurred during the pleistocene epoch of the quaternary period of the cenozoic era of the Phanerozoic eon?
> all modern species of mammals present by end of epoch
Some workers have suggested that chordates arose from?
> arthropods
or mollusks
or annelids
Most workers today agree that chordates have more in common with the _______________?
> Echinoderms
What are the characteristics of the common ancestor of chordates and echinoderms?
> sessile or semi-sessile > deuterostomous > coelomate > bilateral symmetry > ciliated larval form > lophophorates > ciliary feeders
The three chordate su phyla radiated over __________ million years ago?
> 500
What is thought to be basal to the chordates?
> amphioxus is though to be basal to the chordates
» it has been evolving slowly
» a considerable amount of its genome is similar to that of vertebrates
_________ have been evolving rapidly and have discarded many genes?
> tunicates
» tunicates also have a reduced larval body plan
» Ciona (»tunicates are an excellent example of how many genes and how much structure can be thrown away and still have a viable organism
___________ lack some vertebrate characteristics (I.e., immunoglobulin-based immune system, paired limbs, and jaws) have more vertebrate characteristics than amphioxus and tunicates?
> lampreys
Vertebrates switch from _________ feeding (with lophophore) to ____________ feeding with gill slits?
> ciliary
> filter-
Vertebrate descendants include what?
> hemichordates (acorn worms) > primitive tunicates >>> gave rise to: >>>>> modern tunicates >>> larval tunicates forms gave rise to >>>>> cephalochordates >>>>> vertebrates
Amphioxus is the major representative of what subphylum (genus: Branchiostotma)
> cephalochordates
Summarize amphioxus
> the major representative of the subphylum cephalochordates
» found in warm, shallow, marine environments
> > > body forms of both larva and adult is elongated, flattened and tapered at both ends
> > > burrow into sand so that only their head is exposed and filter microscopic food particles out of the water using a ciliary pump and pharyngeal gill slits
> > > larval forms similar to adults but lack gonads
> > > Lack paired fins/limbs and jaws
> > > possess well-developed notochord but no vertebral column
» cells of notochord are stacked flattened discs of paramyosin muscle similar to adductor muscles of clams
» notochord extends from tip of head to tip of tail
> > > nerve cord lies dorsal to the notochord but does not have a cranial enlargement (brain)
> > > lacks cartilage and bone
> > > “V”- shaped muscle segments (myomeres) flank notochord and are used for swimming
> > > cranial end of animal consists of a conspicuous tubular pharynx equipped with a row of pharyngeal slits on either side
> > > mouth opens into pharynx
» gill slits do not open to exterior but into an internal cavity surrounding the pharynx called the atrium
» atrium opens to the exterior via atriopore
> > > a groove, the endothelial, is located in the floor of the pharynx and secreted a thin film mucous that covers the inside of the gill slits and traps food particles and conveys them into the intestine from the pharynx
Members of this subphylum are comprised of three classes, although two of them are seldom observed?
> Urochordates
What class makes of the most common forms of Urochordates?
> ascidiacea
Members of this class of Urochordates are often referred to as sea squirts or tunicates
> ascidiacea
Adult tunicates are sessile bags of fluid and were initially thought to be members of which kingdom?
> the plant kingdom
The adult tunicates lack these two structures, but do have a well developed pharynx with gill slits?
> notochord
> dorsal hollow nerve cord
True or False: larval tunicates have all three chordate characteristics?
> true
An adult sea squirt resembles a small bag with (about an inch in diameter) with two shorty hoses, termed what, coming out of it?
> siphons
» the incurrent siphon leads directly into a large, bag-like pharynx with numerous filtration slits
» the intestine and the atriopore lead to the excurrent siphon
The outer wall of the bag (the tunic or test) of the sea squirt contains a cellulose-like polysaccharide, which is almost unheard of in the animal kingdom. What is the name of the cellulose-like polysaccharide?
> tunicin
The _______, which sits below the tunic, consists of dermal epithelium and connective tissue?
> mantle
How do sea squirts get their name?
> sea squirts get their name because when disturbed they squirt water out of both siphons
How do tunicates draw water into the pharynx through the incurrent siphon?
> tunicates use ciliary action to draw water into the pharynx through the incurrent siphon
Microscopic particles of food material are filtered from the water which passes through the pharyngeal slits into a chamber, the _________, which leads via an _________ to the ___________ siphon?
> atrium
atriopore
excurrent
True or False: waste material from the digestive system and gametes from the gonads are also expelled via the excurrent siphon?
> true
Food particles that remain within the sea squirt pharynx pass where?
> into the intestine
Tunicates developed through ___________ from a tadpole-like larval stage?
> metamorphosis
The other two classes of Urochordates live in open ocean waters and never undergo __________ but remain in a highly modified larval stag capable of reproduction?
> metamorphosis
The larval sea squirt looks like a free-swimming tadpole: what characteristics does it possess?
> a dorsal, hollow nerve cord
a notochord in the tail
pharyngeal gill slits located in the expanded cranial end
True or False: the larval sea squirt is incapable of swimming around until a suitable habitat is found?
> false
> the larval sea squirt. Is capable of swimming around until a suitable habitat is found
What part of the larval sea squirt is responsible for attaching to the substrate once a suitable substrate is found?
> upon finding a suitable substrate, the head of the larva, equipped with adhesive, sucker-like structures, attaches to the substrate
True or False: once attached to a substrate, the tail of the larval sea squirt immediately collapses like an accordion, eliminating the notochord and most the nerve cord?
> true
The __________ ( of the attached, larval, sea squirt) is expanded considerably and takes up most of the volume of the adult?
> pharynx
The remnants of the larval sea squirt neural tube forms a _________ in the adult form?
> ganglion
True or False: once the gonads of the sea squirt develop, transformation is complete?
> true
In the mid-sixteenth century the Swedish botanist Carolus Linneaus developed a system for classifying organisms. What is this system referred to as?
> this system of classification is referred to as the binomial nomenclature system, because it established the practice of taking the genus and species of an organism and designating it as the scientific name for that species
William Hennig in 1966 published __________ _________?
> phylogenetic systematics
» phylogenetic systematics is based on evolutionary lineages called Claude’s (thus it is also referred to as cladistics)
»» a clade is monophyletic group made up of an ancestor and all of its descendants
»» these groups can only be identified on the basis of derived characters
In regards to cladistics, summarize a character?
> character:
» a character is a feature (here, an anatomical feature) of an organism.
> > > a derived character is a character that is different form ancestral condition
> > > derived characters are also referred to as apomorphies
> > > derived characters that are shared by several lineages are referred to as synapomorphies
> > > variations in character are referred to as character traits
> > > ancestral characters that are retained by the descendants of the ancestor are referred to as plesiomorphies
> > > ancestral characters shared by more than one lineage are symplesiomorphies
What is a character?
> a character is a feature (here, an anatomical feature) of an organism
What is a derived character?
> a derived character is a character that is different from the ancestral condition
Derived characters are also known as what?
> derived characters are also referred to as apomorphies
What are synapomorphies?
> derived characters that are shared by several lineages
Variations in character are referred to as what?
> character traits
What are plesiomorphies?
> Ancestral characters that are retained by the descendants of the ancestor
What are symplesiomorphies?
> ancestral characters shared by more than one lineage
What is a clade?
> a monophyletic group made up of an ancestor and all of its descendants
What is a paraphyletic group?
> includes a common ancestor and some but not all of its descendants
What is a polyphyletic group?
> includes descendants but not the common ancestor
What is/are apomorphy (-ies)?
> a derived character
> a derived character is a character that is different from ancestral condition
What are synapomorphies?
> derived characters that are shared by several lineages
What are plesiomorphies?
> ancestral characters that are retained by the descendants of the ancestor
What are symplesiomorphies?
> ancestral characters that are shared by more than one lineage
What is a paraphyletic group?
> a group being discussed that includes a common ancestor and some but not all of its descendants
What is a polyphyletic group?
> a group being discussed that includes descendants of a common ancestor but not the common ancestor
What is a cladogram?
> a diagram that shows a sequential hypothetical evolutionary branching pattern of a group of clades
