Evidence of Vertebrate Life Flashcards
What is our closest non chordate relative
Sea star
Does carbon dating date the fossil itself?
No, dates rocks around it
Oldest living vertebrates
Cyclostomata (round mouth)
Lamprey and hagfishes (jawless fishes=Agnatha)
Have rudimentary vertebrae made of cartilage, not bone. Vertebrae only in embryo in hagfish.
Tetrapods
What is important about their limb bones
Vertebrate with four limbs or- like snakes, birds and whales are descended from vertebrate with four limbs
Limb bones of tetrapods are HOMOLOGOUS
Ray-finned fishes represent _____ of all fished today
95%
Coelacanth
Lobe-finned fish
Only 8 species live today
Our closest relative among fish
Have humerus!!
We last shared a common ancestor with coelacanth _____
400mya
Intermediate fossils of Tiktaalik
Lobe-finned fish (Eusthenopteron)
-385mya
Early tetrapod (acanthostega)
-365 mya
Between fish and tetrapod was needed
How to look for a specific fossil
- Use distribution of known fossils to determine when there was a gap in the fossil record
- Predict where rocks of that age (375mya) are exposed on earths surface
-type of rock
-age of Rock
-location of rock
Narrow range of conditions needed for a fossil to form
-most are consumed, trampled or beaten by weather that nothing is left to fossilize
-soft tissue organism are unlikely to fossilize
-fossil record can never be complete
-have to die in the right place (stream, lake or muddy area)
-fossils usually form when an organism is immediately cover by water (create sedimentary rocks)
-fossils in sedimentary rock are quickly worn away when exposed to the surface (sun, wind, rain)
What percent of dinosaur species is estimated to be known
<1%
Type of rock with most fossils
Sedimentary
High temp of igneous and pressures of metamorphic destroy animal remains
Radiometeic dating: carbon dating
Carbon dating can be used to directly date fossils or sedimentary rock
-carbon daring only works for fossils and rock less than -50,000years (carbon decays quickly)
Other radiometric dating isotopes
Potassium-argon 50,000-4.6Bya
Uranium-lead: 10m-4.6b
How palaeontologists predict where to find fossils
- Type of rock: sedimentary
- Age of rock: geological layer (time)
3.Location of rock exposed on Earths surface: disconnect between past and present (changing lane forms: mountains rise, erode). Need rock exposed on the planets surface, continental drift
Ellesmere Island and continental drift
365 mya during the Devonian period, island was on equator. Now it is 80.7°N
Home of Tiktaalik
Tiktaalik fish and tetrapod features
Large freshwater fish
Fish: scales, fills, delicate ray-finned tail
Tetrapod: flat head, eyes on top, neck moves (head free of shoulders), two wrist bones (Ulnare and intermedium) enable it to do a push up
What does Tiktaalik tell us about why limbs evolved
Anatomical features suggest Tiktaalik lived in water: gills, rays on tail, paddle shaped limbs probably used to pull itself along the shallow water.
Infer: bones that later formed a limb originated for life in water, not because they were useful to animals that already lived on land.
Cambrian explosion
541-515mya
-Sudden diversification of life early in the Cambrian
Pre Cambrian includes which eons
Archean and proterozoic eons
Hadean Eon
4.6bya to 4.0bya
-water present (4.0)
-earth forms; collisions with debris in solar system (4-3.8)
Volcanic eruptions, frequent collisions with other solar system bodies, extreme heat
Archean Eon
4.0-2.5bya
-single celled organism arise
-earth crust cooled
-prokaryotes only
-stromatolites, thermal microorganism
-oldest known bio markers
Stromatolites and when they appeared
Microbial mats; layers of Cyanobacteria and sediments.
-single celled but colonial
-first form of life visible to naked eye
-appeared in archean Eon 3.5bya
-prokaryotes we’re earths sole inhabitants
Deep sea thermal vent microorganisms date back to
3.8bya
-tubular microfossils
Archean
Bio markers
When are earliest found
Molecules produced by biological processes
Ex: DNA traces, lipids, carbon isotopes, oxygen, methane
3.7bya
When was an increase in oxygen found
Ancient rocks show sudden rise in O2 at 2.6by probably result of photosynthesis by Cyanobacteria
Proterozoic Eon
“Earlier life”
2.5bya-541mya (Cambrian)
-life in ocean dominated by microbes (free floating bacteria, hydrothermal vent single celled organisms, microbial mats)
-photosynthetic eukaryotes (algae) at oceans surface (1.6bya)
Eukaryotes arrive!
Eukaryotes
Nucleus surrounded by a membrane
Plants, animals, fungi and protists (single celled eukaryotes)
Toward the end of the Proterozoic eon, we see fossils of ______ and ______
Sponges and cnidarians (jellyfish)
Sponges are earliest evidence of animals (650mya)
When was the oldest evidence of animal tracks found (eon)
Proterozoic
585mya
Ediacaran period
635-541mya
First explosion of complex life
-invertebrates (probably)
-most were sedentary
-
Cambrian period
-eon
-date
-purpose
-explosion timeline
Phanerozoic eon
541-485mya
-moving animals, predators, decrease in ediacaran species
541mya -new life forms that we recognize today
When most of the phyla of animals that are still alive today appear! Include us the chordates!
Phanerozoic Eon
Visible life
541 mya-present
4 Eons
Hadean
Archean
Proterozoic
Phanerozoic
Animals that appeared during the Cambrian had a body plan similar to that of many invertebrates and vertebrates living today… including…
Bilateral symmetry
Heads and tails
Segmentation
Mobility
The first major excavation site for the Cambrian fauna was at…..
Burgess Shale, BC (Rockies)
Sea bed pushed upwards into mountains
Possible reasons for Cambrian explosion
-genetic revolution and movement (HOX)
-increase O2 permitted animals to be bigger
-arms race (predator-prey)
-increased nutrients due to sea level rise
Colonization of lane over time
Step by step
1bya-Cyanobacteria and photosynthetic prokaryotes in damp terrestrial locations
500mya-fungi, moss-like plants
450mya-arthropods were the first animal group
365mya-early tetrapods (first vertebrates on land
3 eras in the Phanerozoic era
Paleozoic
Mesozoic
Cenozoic
Paleozoic era
-cambrian explosion
-chordates and vertebrates appear
-Devonian: vertebrates move to land
-Permian mass extinction (252mya)
541mya-252mya
Mesozoic era
-k-pg mass extinction: 65.5mya, dinosaurs die (except birds)
-mammals live in shadows of dinosaurs
252-65.5mya
Cenozoic era
Recent
Mammals diversify
65.5mya-present
Mass extinctions
Catastrophes that influenced vertebrate evolution
Eliminate certain groups
Enable other groups to survive and diversify
5 identified since start of the Cambrian
End of Devonian extinctions
Extinction led to explosion of which groups
Two extinctions near the end of the Devonian (Paleozoic)
-last extinction eliminated 44% of jawed vertebrates, many lobed-finned fishes, and most of initial tetrapods
Expansion of ray-finned fishes and cartilaginous fishes
Permian extinction
Eliminated the largest proportion of species of any extinction to date. Referred to as “the day when life nearly died”
-during the last period of the Paleozoic era, with the Triassic periods of the Mesozoic era beginning. (252my)
-eliminated 57% of marine invertebrates (trilobites too), 95% of Marine vertebrates.
-massive volcanic activity led to runaway greenhouse gas effect with global warming and ocean acidification
Took 5 million years to recover
After recovery from the Permian extinction, what group took over
Dinosaurs
K-pg (KT) extinction
Cretaceous-Paleogene extinction
During end of Cretaceous period (end of Mesozoic era)
-most famous extinction
-large asteroid hitting earth (Yucatan peninsula)
-extinguished all non-again dinosaurs and other large vertebrates
-volcanic activity contributed
65.5mya
Following the K-pg extinction, what group took over
Mammals
Are we in the middle of the 6th mass extinction?
-habitat loss
-over hunting
-pollution
-increase co2 and green house gases
-ocean chemistry
Most current vertebrates are above the background extinction rate
Anthropocene
Present world
How humans have altered the world
Chordates share which important aspects of their body plan with bilateral invertebrates (clade Bilateria)
Bilateral symmetry
Anterior-posterior axis
Cephalization (anterior head, posterior anus)
Mobility
3 germ layers
Types of symmetry
-asymmetry (sponges)
-spherical symmetry (divide body in equal halves by any cut through center)
- radial symmetry (symmetry around central axis-hydras, jellyfish)
-bilateral symmetry (Sagittal cut makes mirror image-buts, fish)
LCA
Last common ancestor
When did the bilaterians arrive
600mya
Bilaterians have ____ germ layers
This means they are called ______
3
Triploblastic
Coelom
Body cavity within mesoderm
Do flatworms, nematodes, mollusks or annelids start the coelom
Nematodes
Which groups have a true coelom
Do molluscs count?
Annelids, arthropods, chordates
No, reduced coelom
What groups of metazoa are deuterostomes
Chordates
Echinoderms
Gastrulation
- Formation of the gut
- Also used to describe formation of germ layers
-cells from outer layer (ectoderm) move inward to form endoderm (inner layer)
Diploblastic animals have how many germ layers
2
What does deuterostomes and protostomes mean
Mouth second (first opening formed during Gastrulation is the anus.
Mouth first
Mesoderm
-Third germ layer to arise in Triploblastic
-middle layer
-arises from endoderm
-once formed, a new cavity arises from it (coelom)-fluid filled cavity lying within the mesoderm.
At 4 weeks of conception, we have a ____ within a _____ with three germ layers that give rise to ______
Tube (gut)
Tube (coelom)
All our organs
Chordates and most bilateral invertebrates (annelids, arthropods, echinoderms and Hemichordates) have ______ germ layers and a _____
3
Coelom
Coelom def
The coelom divides into which 3 body cavities
Fluid filled cavity lined by mesoderm on either side
-pleural cavity (encloses lungs)
-pericardial cavity (heart)
-peritoneal cavity (organs within abdomen: intestines, liver)
Advantages of having a coelom
Space for organs to grow and fallibility in their arrangement
Fluid filled cavities cushion organs which help to prevent injury
Endoderm
Mesoderm
Ectoderm
Main differentiated tissues of each
-Lung or hill linings
-most of the digestive tract
-bone, cartilage, muscles, circulatory, Urogenital systems (gonads, blood)
-skin cells of epidermis
-pigment cells (neural crest)
-most of the nervous systems
-antihero and posterior digestive tract (mouth and anus)
Embryonic cells unique to vertebrates that is considered a 4th germ layer?
Neural crest cells!
Forms from ectoderm, lateral to neural tube; separates after nerve tube forms
Considered 4th germ layer
Gave rise to structures unique to vertebrates: certain bones and cartilage of face and skull, adrenal gland, pigment cells, para-and sympathetic nervous systems
What is another embryonic tissue unique to vertebrates?
Placodes
-form from ectoderm and migrate elsewhere in the body
-give rise to sensory and cutaneous structures (eyes, nose, ears, hair, teeth, feathers, anterior pituitary)
Segmentation or metamerism and example
The body being constructed in a linear series of relating parts, each formed in a sequence in the embryo, from anterior to posterior
Vertebrate development
Myomeres, ribs, vertebrae
Metamerism is a shared characteristic with animals that have a _____
True coelom (annelids and arthropods)
Somites
Developing segment (in embryo)
-develop from mesoderm in the embryo along anterior-posterior axis
Segmented (somatic) mesoderm forms structures that are repeated (axial skeleton and axial muscle)
Mesoderm that is not segmented, forms structures that are ______
Not repeated
Metamere
One segment of repeated body segments in animals or plants
Annelids, arthropods and chordates have bilateral characterisitcs as well as
A true coelom
Matemerism
In what stage do embryos have the defining features of chordates
Pharyngula or phylotypic (pharyngeal pouches visible)
Shared feature develop early
Derived features develop later
Mangold-Spermann experiment
Two salamander eggs in Gastrulation stage. One egg has piece of dorsal lip (ectoderm invades endoerderm) taken and put onto another egg. Second egg develops a second embryo at the site of transplant, consisting of the donor and recipient cells (different pigments)
Conclusion: a cells fate is not predetermined at the time of fertilization
Old view of genes
Each gene has a specific trait it determines such as an arm or eye
Therefore organisms that are more complex should have more genes
Human chromosomes and protein coding genes
3600 genes are continually expressed in all cells as basic cellular process genes
14200 genes required in some tissue at certain times though not others
New understanding of genes
Gene-regulatory networks
-expression of a few genes triggering or inhibiting the expression of downstream genes or molecules
Genes that regulate development are known as
Homeotic genes or developmental regulatory genes
_______ genes and other ___________ interact in hierarchical networks that shape the geography of developing animals
Hox
Developmental regulatory genes
First homeotic gene to be discovered
Hox
Homeotic transformations in fruit flies are caused by defects in ______
Single genes
Ed Lewis gene hypothesis and explanation
Single gene determines the type of Boyd segment (true)
Every cell in an organism Carrie’s, within its DNA, all of the information necessary to build the entire organism, but not all the info is expressed in every cell.
Antp (Hox gene) expressed where causes what
Expressed in thoracic area causes legs to grow at right palce
Expressed on head causes legs to grow in place of antenna
Genes are position on the chromosome in the order that……
They correspond on the final body plan
Hox genes either ______ or ______ downstream genes
Allow
Suppress
If hox gene Antp is activated in the head, genes coding for antenna are suppressed but the gene Distalless is expressed causing a leg
Hox genes are arranged along the chromosome in the same_______
Spatial and temporal order in which they are expressed
How many hox genes and chromosome do mammals and fruit flies have
39 Hox genes on 4 chromosome (paralog genes of mammals from duplication events)
8 Hox genes on 1 chromosome
Hox genes are homologous to both!!!
Why will Hox genes in flies be expressed but rarely in mammals
Has 1 copy
Has many copies (paralogs) of same Hox genes that can overrule the mutation
Spatial and temporal sequence of Hox genes in a mouse embryo
First, anterior hox gene is expressed which corresponds to the neck (cervical)
Then, another hox gene is expressed that corresponds to throrax
Finally, another hox gene is expressed and corresponds to lumbar vertebrae
Duplication and loss events
Duplication of Hox genes in vertebrates
Fish have huge amount is genes but fewer chromosomes suggesting a less of clusters
Are Hox genes only in vertebrates?
No
Plants and jellyfish (invertebrates) too
Eyeless gene and major breakthrough
Fruit fly grew a normal fruit fly rye from a mouse “eyeless gene”
Same genes!!!! Universal set of genes!!
Chordates have more hox genes in what area compared to flies?
Lumbar
Ortholog
A homologous gene in different taxa
Mouse Pax6 initiates formation of _____ on fruit fly, on any body segment where it is expressed
Pax6 (eyeless) is homologous across _________ and ______
Eye
Codes for “eye” not for the specific form of eye
Vertebrates and invertebrates
Mouse and fruit fly eyes can develop from either of each species genes, meaning that the genes are ________
Homologous
Inherited from a common ancestor
Genetic cascade for fruit fly limb
Engrailed (En) is at the top of the hierarchy. It defines the posterior part of the limb in flies and in mice.
Hedgehog: in both flies and mice, expression of En turns on a signalling gene called hedgehog in those posterior cells ( the gene is known as sonic hedgehog in terrapods)
Dpp, Wg: Hh protein rhen diffuses into cells that En does not reach. By doing this, a high concentration of Hh causes cels to being expressing two additional signalling genes (Dpp and wingless (Wg))
These genes then initiate one more level of gene activity (D||, EGFR) the combination of these scrabble maps out the geography of the limb in all its dimensions
Fruit fly limb genes and mouse limb genes
Same cascade, different names due to people not knowing they were the same
En (Engrailed) in both
Hh=Shh
Dpp=Bmp
Dll=Dlx
EFGR=FGFs
In tetrapods like mice, limb and digit development is arrested when _____ expression is blocked
Sonic hedgehog
Too little Shh=fewer digits
Too much Shh=additional digits
Shh turns on at the same location of a ______ and a ______
Fin and a limb
Shh (Hh) function
Left-right body axis; Sitka/proximal limb axis, feather formation, brain development
Dlx, Dll (distalless) function
Jaws, limbs, colour patterns
Pax6 (eyeless) function
Eyes, sensory organs, certain neural tissues
Bmp (Dpp) function
Bone morphogenetic protein: bone formation; cell division and death; dorsal-ventral axis
What varies to create diversity in genes
- Location (Heterotopy): where gene turns on
- Timing (Heterochrony): when gene turns on or off, or duration
- Level of expression (Heterometry): amount (level of gene expression)
How do snakes form the long body
- Long body: accelerated formation of somites results in >300 vertebrae
- Thoracic Hox6 gene expressed over large number of vertebrae, resulting in ribs over a large reason and suppressing fore limb development
3.Hind legs: limb bud forms but Shh is not expressed, preventing further growth
Increased expression of Dpp results in _________
Bmp2 responsible for ________ in bats
Long hind limbs of crickets
Long dividers on fore limbs of bats
Webbing on duck feet and no webbing on chickens
Genetic traits
Cell on distal tip of forelimb produce high levels of Bmp2
Gremlin inhibits loss of webbing between digits in embryo (bat wing, duck foot)
Vertebrates develop fingers and toes with webbing initially. But death of cells removes most webbing.
Genes from bmp family result in the loss of webbing between digit in animals. Gremlin suppresses the loss of webbing between digits in embryo:
Dog skull and genes
Increased expression of Runx2 increases BMP, which affects length and shape of carnivore skull and snout
What genes are important for eyespots on butterfly wings
En
Dll
Antp
Traditional classification and taxonomy system
Linnaean system
Hierarchial system: phylum, class, order, family, genus, species
Binomial nomenclature
Phylogenetic systematics or cladistics
Produces hypotheses about the evolutionary relationships of organisms in a way that weighs the relative importance of different characteristics
Clade
Monophyletic group
Evolutionary lineage containing the last common ancestor of all members of the group and all of the ancestors descendants
Cladogram
A visual representation of the evolutionary history of species, populations or genes
Phylogenetic tree
Shows the evolutionary history, but also includes data on the evolutionary time scale
Cladogram parts
Root
Nodes
Branch
Tip
Time axis
Base of the tree
Are points in a phylogeny where a lineage branches (represents a last common ancestor before a speciation event
Lineage evolving through time that connects other branching events
The terminal end of an evolutionary tree (representing) the groups being compared)
Ancestral states (earlier), derived states (more recent)
The taxonomic groups included on a cladogram can be switched around, as long as…..
They are rotated around a particular node
Common misconception about cladograms tips
No current living species is ancestral to any other!!!!!
Clades are ______ within other clades
Nested
Apomorphy
Derived trait
Synapomorphy
Where is it marked
Derived character shared by members of a Clade, not found in an “outgroup”
Marked before branch (LCA)
Autapomorphy
Where is it marked
Derived character unique to one Taxon
Drawn as a line after LCA
Examples of vertebrate synapomorphies when compared to amphioxus
Skull, expanded Brain and vertebrae
Pleisomorphy
Symplesiomorphy
Ancestral character
Ancestral character shared by members of a group (character that ancestor/ outgroup had that all other members have too)
Outgroup
Ingroup
A reference group that is less related to the taxa we are comparing
The organisms you are studying
A change in a phylogenic tree can mean what?
Gain or loss of a trait
Any change from the ancestral species, or from an outgroup, is defined as a _____
Derived character
Which cladogram do you select?
The one with fewest steps/ changes
Principle of parsimony (Occam’s razor)
The simplest hypothesis is the most plausible
How do you know which species are more closely related by looking at a phylogenetic tree
Two groups that share a last common ancestor more recently are more closely related
Clade (Monophyletic group)
Contains the last common ancestor of all members of the group and all of that ancestors descendants
Paraphyletic group
A group of organisms that share a common ancestor, but the group does not include all of the descendants of that ancestor
Paraphyletic groups involve what we refer to as _____ and _____ groups
Stem: extinct forms that lack some of the derived characters found in a crown group (non-avian ancestors of birds)
Crown: Has deceived characters of extinct species in group; includes extinct species that contained those derived characters, but not the stem group
Polypheletic group
A group that does not include all ancestors of the species
If looking at evolutionary relationships you need:
If looking at a particular group that may include the crown group, you need:
If looking at the origins of a train that occurs in different groups (convergent evolution) you need:
Monophyletic
Paraphyletic
Polyphyletic
Phylogenetic bracketing
Cladograms to test hypotheses
Birds and crocodiles form phylogenetic bracket around dinosaurs
Did dinosaurs have parental care?
Most likely
- Phylogenetic bracketing suggests parental care may be ancestral trait for the Clade including dinosaurs
- Fossils
Examples of natures imperfections
Hernias
Hiccups
Blind spot in the vertebrate eye
Circuitous rout of the recurrent laryngeal nerve
Inguinal hernias
Most common abdominal hernia and mostly occur in men
-testicles start to develop close to heart, but move to scrotum. Testes travel through a canal-called the inguinal canal to descend into the scrotum.
-after the testicles descend, the opening is supposed to close tightly, but sometimes the muscles that attach to the pelvis leave a weakened area in the body wall.
-if stress is placed here…the weakened spot of the body wall will allow a portion of the intestine to slide through that opening into the scrotum, causing pain and producing a bulge!!!
Recurrent laryngeal nerve
-inner area larynx and muscles related to swallowing and breathing
-travels from brain along neck down near heart, then to larynx
Vagus nerve in fishes
Vagus nerve and it’s branching travel directly from brain to gills (along the dorsal artery) to help muscles pump water.
Four branches of the vagus nerve are around the gills
4th branch of vagus nerve is called what
Recurrent laryngeal nerve
Inner area the larynx and role in swallowing
What is odd about the recurrent laryngeal nerve
Instead of going straight from the brain to the larynx, it goes all the way to blood vessels that are derived from the 6th arterial arch just like in fish!
The nerve in giraffes is 6 meters long
Where does the RLN go in humans
From brain to under the aortic arch (blood vessels derived from 6th arterial arch of fish) and back to larynx
