Studied by 0 people
Why is homeostasis a vital feature of life?
Organisms are under strong pressure to develop ways of balancing the need for ideal conditions with the practical realities of the environments they actually live in.
What is homeostasis? Is it the only option organisms have when their environment becomes less than ideal?
The maintenance of internal conditions as close to the ideal as possible. No; the organism can also cope with the change and live un-ideally for a while.
What are key terms associated with homeostatic systems?
Set Point: a subset of conditions optimal for the body and that will be maintained.
Rules: Guidelines the body has for what these set points should be for regulated things.
Stimuli: something that drives a fluctuation outside of the set point.
Response: a physiological activity that pushes the body back towards a set point.
What are positive and negative feedback loops? What do they exist to do?
Negative feedback loop: get anxious → feel bad → do something constructive → remove anxiety
Positive feedback loop: try hard → fail → get frustrated → feel bad → try hard → etc.
These systems exist to create or maintain homeostasis for the organism.
What is thermoregulation? Why would an organism thermoregulate? What are the two approaches to do it? How do the terms endo- and ectothermy differ from homeothermy/poikilothermy?
Thermoregulation is the maintenance of homeostasis around a set temperature point.
Three reasons to thermoregulate: Keeps an organism’s chemical environment stable, Warm but not hot temperatures are good for fast reactions, and It’s also best if our membranes are fluid but not too fluid, so warm temps are good for that too.
What four things must a thermoregulator be able to do?
4 things thermoregulators do: Release excess heat, Resist excess heat, Acquisition/Production of wanted heat, and Prevention of wanted heat loss
How do animals shed excess heat?
Vasodilations (making our exterior vessel bigger)
Encouraging evaporation
Shedding insulation
How do animals avoid excess heat?
Being calm
eating/digesting less
Moving away from heat sources
Insulating
How do animals make/generate excess heat?
Cuddling!
Shivering!
Upping your metabolism
Sunning
How do animals prevent loss of excess heat?
Vasoconstriction (the narrowing (constriction) of blood vessels)
Modifying your surface (e.g., ruffling you feathers)
Hiding from air/water flow
Insulating
Reviewing the animal phylogeny for Sharks and Bony Fishes
Derived from chordates (vertebrates)
Lampreys and hagfish have vertebrae and cartilage skeletal elements but not internal bones or jaws (cyclostomes – circle mouths)
All other vertebrates have both (gnathostomes – jaw mouths)
Why developing a jaw was a big deal
Before jaws:
Stuff would go in your mouth all the time whether you wanted it to or not (or nothing would go in at all?)
You couldn’t chew anything into smaller pieces before you swallowed it.
If something you had swallowed wanted to wriggle out, it could do that.
Where did jaws come from?
We think they evolved through the recycling of gill arch rods.
For the gills to function properly (catching food to swallow it and still allowing excess water to flow through the gills).
They had to have some kind of structure to allow for this to occur. So, the gill arches served as a structure for keeping them open.
Eventually, the gills evolved for another purpose (gas exchange). There was no ned for the original purpose of those skeletal rods.
This allowed the gill rods to be free to develop into the jaws.
The other key features shared by gnathostomes
Another duplication of the Hox genes (2 to 4).
Enlarged forebrain relative to other regions (More complex thoughts and actions); Deliver more oxygen to the brain allowing for an increase in size of the brain.
Improved vision, smell, and hearing.
Jaws were likely responsible for the last two due to gas exchange developing and moving to be better eaters.
The key features and facts of the Chondrichthyans
Skeletons predominantly made of cartilage but with some calcium
The cartilaginous-based skeletons have to give them some type of advantages… comes down to weight and density. Moves at greater speeds.
Derived a loss of cartilage.
The key features of and clades within the Osteichthyes
Two Subclades
Ray-finned fish
Lobe-finned fish: Coelocanths, Lungfish, and Tetrapods!
All have an ossified skeleton
Lungs or lung derivatives
The key similarities and differences between the three major clades of extant bony fish.
Ray-finned fish: bones in fish are mostly rays
Coelacanths: use fully articulated fin bones; Flesh-covered rather than thin fins with thick muscles associated with true bones
Lungfish: Freshwater habitat; Use lungs instead of gills; Secondarily derived characteristics: swim bladder with oil instead of air from buoyancy
The tetrapod forelimb
Same forelimb and rear limb morphology for all tetrapods. Never changed since essentially the Tiktaalik. You will still follow one bone, two bones, lots of blobs, and digits.
What characteristics do tetrapodomorphs have?
Similar morphology to true tetrapods (and even include them too!)
Structure of all tetrapod limbs: one bone, two bones, lots of blobs, and digits.
Tiktaalik: an organism that could lift itself out of the water and turn its head; shoulder association; more evolution of what became the tetrapod lineages.
What is the derived characteristic of tetrapods compared to tetrapodomorphs?
Tetrapods are the first animals to have true digits.
You must have true digits to be considered a tetrapod. No longer encompassed in a paddle. Acanthostega are first true tetrapods by this definition.
Same forelimb and rear limb morphology for all tetrapods. Never changed since essentially the Tiktaalik. You will still follow one bone, two bones, lots of blobs, and digits.
What drove the evolution of tetrapod skeletons?
Buoyancy of fish allows for a weaker skeleton with different articulations, but tetrapods evolved to live on land
Water is denser than air and can help support a body and be a medium against which to push for locomotion; tetrapods evolved to overcome gravity since they had to combat air instead.
How do tetrapods deal with gravity?
Pelvic and pectoral girdles – support and articulation for limbs
Digits for gripping and pushing on land
Every form of locomotion that tetrapods undergo means that all have some form of digits.
Necks of 1 or more vertebrae.
No gills as adults… mostly
Gills become ears, glands, and neck structures.
What are the distinguishing characteristics of amphibians?
Have bi-phasic complex life histories (how we describe the biologic needs of a double-phase organism that undergoes a metamorphosis); Some skip the larvae and undergo a form of direct development
Require moist conditions for eggs; Most amphibians breed in water; Those who breed on land (or underground) require constant moist conditions or their eggs will desiccate.
Moist, permeable skin acts as a respiratory organ.
General characteristics of frogs and toads
25% discovered in the last 15-20 years
Most have a fully aquatic tadpole stage that are herbivores
Labial teeth and jaw sheath – use teeth for suction and jaw sheath for scraping.
Some are direct developers
Become predators as adults; that transition commands that you have a dramatic transition of your gut physiology.
They went from digesting cellulose-rich plant material to chitin-rich insect material.
Influences locomotion by improving thrust to rear limbs. Twisting muscles and bones that aid in their movement.
General characteristics of salamanders
They have a larval and a juvenile/adult phase
Terrestrial, fossorial, and fully aquatic species.
Predators in all life stages
How do lungless salamanders breathe?
They use cutaneous gas exchange as their sole form of breathing.
General characteristics of caecilians
Burrow or are fully aquatic; come out for one or two days a year to breed and burrow again. Limbs lack bones and articulations; no pectoral girdles. Thought that the girdles are lost for increased mobility and agility. Most lack eyes.
Tentacle – chemosensory organ.
Senses the chemicals in the environment
Many do cutaneous gas exchange; however, they typically retain their right lung (not the left)
Can have direct development in eggs or inside the female as live young or eggs.
Dermophagy – Ingestion of your mother’s skin soon after you’ve hatched.
What is metamorphosis?
Process where juvenile organisms undergo a morphological and physiological body reorganization to become adults.
In frogs: limbs develop and tails are reabsorbed, gills are reabsorbed and lungs (or skin) become the primary location of gas exchange.
What is paedomorphosis?
Becoming sexually mature while still retaining juvenile characteristics.
For example, some salamanders become sexually mature while retaining juvenile skin, mouth, and gill morphology
Obligate vs. Faculative
Obligate – they must stay as juveniles; you can’t leave the aquatic environment.
Facultative – maintaining a juvenile form by choice.
What are the key features of the amniotes?
Most reptiles are able to live life predominantly outside of water
Protective layer around your offspring to keep them in ”water”
Better egg, incubate internally.
They don’t need a bi-phasic life cycle (no need for larvae to swim)
Have lungs and rib-attached lung muscles (negative breathing)
They don’t need to breathe through their skin (and their skin is more waterproof and tough) Have an armor that doesn’t cost a lot to produce or carry around
Limbs built for better upright locomotion; helps decrease the amount of body in contact with hot surfaces.
They have a LAND egg, not a FISH egg.
What does each part of the amniotic egg do?
Amnion – fluid keeps the animal hydrated and protected
Allantois – waste is collected and sequestered away from animal
Yolk sac – food resource that depletes as embryo develops
Chorion – gas exchange; outer layer around allantois important for gas exchange. Allows gases in
Albumen – protein rich shock absorber
Shell – intruder barrier and keeps water in.
What are temporal fenestrae? What the heck are they for?
Holes in the side of the skull
Two groups: synapsids and diapsids
Mammals are synapsids due to the evolutionary loss of one of them
Attachment points for the jaw muscles = having points of attachment increases the strength of the jaw
Why is the amniote phylogeny messy?
Lots of polytomies – not sure of all relational connections; we also have no idea where to put turtles
You also have to include extinct taxa to see the origin of other organisms
What are the key features of the diapsids (the reptiles)?
They do thermoregulate ectothermically mostly, but some may be endothermic.
Leathery, or hard-shelled eggs
Scales of keratin (not bone-like minerals)
Extant reptiles: Turtles, Archosaurs, and Lepidosaurs.
Who are the turtles and what makes them interesting?
Most have shells fused to their spines, ribs, and collarbones. (Scutes). Rewrite the entire skeleton of turtles; attach to the spine, ribs, and collarbones.
Shells are made of bones and covered in keratin scales; they have the strangest locomotion because of this
They have no teeth but have beaks.
Temperature-dependent sex determination
Two major groups:
Pleurodira – side-necked turtles
Cryptodira– telescopic neck turtles
Which reptiles are lepidosaurs? What features define this clade?
Tuataras – sphenodontidae
Squamates – snakes and lizard
Many use scales to undergo locomotion
Keels – textured central stripes that increase grip as they move through the environment. They are also great at smelling but have a lower capacity for eyes and ears.
The way Pangea broke created tuataras
Many are limbless
Which reptiles are archosaurs? How is this clade interesting?
Crocodilians, Pterosaurs, and dinosaurs.
This group includes the pterosaurs, the first deuterostomes capable of flight.
It also contains the dinos, the terrifying reptiles. Our mental image of the dinos is pretty inaccurate in most respects.
Pterosaurs still have the structure of the skeletal system discussed in Shubin
Birds have specialized flight modifications
Ornithicians – bird-like pelvis; bent walkng posture
Sauricians – more upright pelvic positioning.
Many were social, had feathers, and brooded their nests.
How do you tell apart crocodilians?
Warm climate, aemi-aquatic archosaurs.
They’ve reverted to the ancestral tetrapod body after becoming bipedal. Reason why we think this is so is by observing the pectoral and pelvic girdles.
Crocodiles – V-shaped mouths (salt and fresh water)
Alligators (caiman) – U-shaped mouth (fresh water)
Gharial – elongated slender mouths (fresh water)
Where do birds fit in the amniote phylogenetic tree?
All are endothermic – all can internally thermoregulate
Highly derived saurischian dinosaur (flight)
They had to gain flight by taking off from high cliffs; they could escape from predators that couldn’t follow them off of high cliff areas.
There was a lot of simultaneous development during the time of the dinosaur.
Who was the first bird species?
Earliest bird: archaeopteryx (160 million years)
Why fly?
Flight is costly
Redesigned body efficient for flight
excellent sensory system (ESPECIALLY vision)
Motor control of powerful muscles and considerable
efficient circulation and respiration
Advantages
You can attack from above where things can’t see you
You can cover more ground aerially
You could scavenge; your opportunity is raised for finding food
You can catch flying insects.
You can escape predators
You can lay your eggs somewhere safer.
You can migrate.
What are the defining characteristics of flight?
Requires fine motor control of powerful muscles and considerable brain power.
Requires excellent senses (especially vision).
Also requires a great circulatory and respiratory system.
Adaptations
Double breathing; increases the amount of oxygen that can be taken in by the birds
Hollow, honeycomb-like bones; have a crosshatching to add structure to a lightweight bone
Feathers for more than thermoregulation
Lost teeth because teeth are so heavy comparatively; series of modifications to allow for this
No bladder; sent out of cloaca immediately after being digested; liquid is heavy
One ovary; generally female birds will lay eggs one at a time to decrease the amount of body weight and allow for better survival
Gonads are tiny outside of breeding season; more lightweight if you only invest in reproductive tissue during breeding season
Contoured feathered wings
How are bird limbs adapted for flight?
Digits remain quite small
Down feathers for warmth only attach in the skin
Feathers have a hollow shaft and goes down the center; blood during development of feather
Barbs and hooks are responsible for creating a solid air-defying structure.
Feathers that are farther out are more likely to have a more rounded feather; changes how air is captured and facilitates as much air being captured under the feather at all times
What’s the difference between altricial and precocial young?
Altricial – cannot thermoregulate on their own and must be brooded by a parent; will not have their eyes open for multiple days-weeks. Require a lot of parental care to rear; however they are able to hatch quicker, meaning the foraging happens sooner.
Passeriformes – songbirds (6500 of 10000 altricial young.)
Precocial – hatches with the capability for opening their eyes, walking themselves, and finding resources led to by parent; you can leave your nest immediately.
Examples of giant birds
Ratites: giant, flightless bird
Moa; native to south pacific; early settlers decided to eat them (extinction)
Haast’s eagle
Condor
Argentavis
Secondary loss of flight
Some birds have secondarily lost flight
They just simply may not need it.
They may lose it because cost of flight is high.
Why some flightless birds have small pectoral muscles and other have large pectoral muscles
Penguins have strong pectoral muscles because they have to swim
Others may not need them due to not having to use them as the method of locomotion
It’s all going to depend on necessity vs. cost
Songbird adaptations
Songbirds are especially capable
High control of syrinx – vibrate membranes in their throat.
They have perching feet – anisodactyl
Only have altricial young
Generally, all have 12 retrices (tail feathers); evidence for common ancestry.
How do mammals fit on the phylogenetic tree?
A lineage of the amniotes - synapsids
What are the defining traits of mammals?
Insulation and high metabolic rate with endothermy
Some form of parental care must be present within every species member.
All have hair and fur as well as a fatty layer directly under the skin; fat is distributed differently in other species
Four-chambered heart; ventricles are separated
Larger brain-to-body size ratio
Variety of teeth (canines, molars, etc.)
Kidneys are more efficient, increasing waste removal and allowing even better endothermy.
What is the major difference between monotremes, marsupials, and eutherians?
Monotremes - non-therian mammals → oviparous (egg-laying)
Marsupials - Therian mammals → viviparous (birth to an embryo)
Eutherians - Therian mammals → viviparous (give birth to infants)
General Monotreme characteristics
Exclusively southern hemisphere
Platypus and echidna
Egg laying and secrete milk through pores
Echidna have modified hairs that make up the spines
General Marsupial characteristics
Opossum – only marsupial north of Mexico
Many have pouch in front, greater bilby = burrowing animal pouch in back to protect baby from dirt
Convergent evolution – marsupials and eutherians
Viviparous – give birth to live young
Nipples and placenta (not the one we see in other mammals)
Embryonic development happens in a pouch
General Eutherian characteristics
Gone through all developmental points to be considered a juvenile, not an embryo, at the time of birth.
More complex placenta than the marsupials.
How is a placenta similar to an amniotic egg?
Mother rearranges her entire internal body system to make way for holding the baby (no need for the shell or the albumen due to this)
The amnion and the chorion remain, and they are what rupture during birth, the water spilling from within. (Water broke)
The allantois and the yolk sac (and even some of the chorion) are associated with the umbilical cord, the center of connection between mother and embryo.
What are the major clades of mammals?
Xenarthrans
Primarily South America and have joints rarely found in other mammals.
Afrotheria
Primarily Africa. Have strange teeth shapes and use their mouths/trunks/teeth to eat, not limbs.
Laurasiatheria
Primarily Northern hemisphere. Often large, highly mobile, and have cool and diverse limbs
Supraprimates
Mostly small + herbivorous, great at climbing/hiding, have short but powerful legs, and we all prominently use our incisors for eating (“cutting” teeth).
How does our system of hearing similar to ones other animals use to sense gravity?
we think our ability to hear is an exaptation--a re-appropriation of tools that helped early animals do something else, and that something else was not sense sound but rather gravity!
What are the parts of the ear? What role does each play in hearing?
Outer ear – pinna to the auditory canal; simply for hearing;
Middle ear – tympanic membrane (malleus, incus, and stapes);
Inner ear – rest of ear; takes the waves and through a series of canals associated with the cochlea, they turn the waves into something the auditory nerve can send as an electrical signal to the brain.
The inner ear has components associated with pressing down on cilia to balance our body.
Where did mammalian middle ear bones come from?
The stapes is as far back as in Acanthostega (one of the first tetrapods); it simply existed.
The reptiles that have ears use the stapes as a hard structure where sound waves can be transmitted.
Greater acuity of the stapes structure by adding incus and malleus are evolved from bones in reptilian jaw.
Gill rods → gnathostomes → stapes and jaw bones in reptiles → stapes, incus, and malleus
How do sound waves get transmitted to the inner ear?
Soundwaves strike the pinna → funnels the soundwaves into the auditory canal from multiple connections → vibrating through canal → strike tympanic membrane (flexible portion that amplifies sound) → articulates with the malleus → malleus strikes incus → incus sits on stapes → stapes meets with oval window (connects middle ear with inner ear) → cochlea takes soundwaves and creates a signal that your brain can interpret as sound
What other things can our inner ears sense? How?
Acceleration, tilt, and position relative of gravity.
Use a gel like fluid inside of interconnected postules (cupula)
Force of bending – acceleration
Direction of bending – tilt relative to “down”
Depends on the way the gel pushes the hairs (e.g., “getting dizzy”)
What is a lateral line system? What connections does it share with our system for hearing?
Series of cupulas that have a series of sensory hairs that can sense vibrations.
Cupula are detecting “water on the outside”; we use the cupula to detect ”water on the inside”
We think that the use of ear hairs and cupula is ancestral.
Where are primates on the phylogenetic tree and what major divisions exist in primates?
Primates are most closely related to Rodentia (rodents) and Lagomorpha (rabbits, hares, pica)
What are the defining characteristics of primates?
Digits that have flat nails, not claws
Digit muscles and joints for clenching
Fingerprints
Offset sometimes opposable digit
Forward facing eyes
Exceptional hand-eye coordination
Relatively large brains
60% are now threatened with extinction and ~75% have declining populations
General characteristics of Strepsirrhini (vs. Haplorhini)
Strepsirhines have longer snouts, smaller brains and a more highly developed sense of smell than haplorhines
Strepsirrhini
Having large eyes – likely a trait that was in the common ancestor of all primates; they are primarily nocturnal. Bounces light back and forth in the eye to get as much information as possible.
Rely on wet noses for scent marking
Lemurs super diverse (95% threatened with extinction)
Haplorhini
Suborder haplorhini, infraorder tarsiformes – only one genus, TARSIERS
Southeast Asian forests
Dry nose, eyes close together, no tapetum etc
Each eye = larger than their brain!
Faunivorous – eat no veggies
Strepsirhini, which means "twist-nose," characteristics include:
snout-like nose
wet rhinarium (naked, moist area of skin on the snout--think dog nose)
heightened sense of smell
prominent whiskers
divided upper lip tied to the gums by a membrane
wooly fur
grooming claw
dental combs (tooth comb)
Haplorhini, which means "simple nose," characteristics include:
relatively flattened faces (when compared to Strepsirhini)
forward facing eyes
postorbital enclosure (bony plate encloses back of eye socket)
dry noses
decreased reliance on sense of smell
larger brains and body size (when compared to Strepsirhini)
diastema (space between upper lateral incisor and upper canine tooth) except in humans
increased gestation, maturation, and parental care
more mutual grooming
General characteristics of tarsiers
Southeast Asian forests
Dry nose, eyes close together, no tapetum etc
Each eye = larger than their brain!
Faunivorous – eat no veggies
Name due to large ankle bones.
General characteristics of Platyrrhini (vs. Catarrhini)
Using eyes more
New world monkey
South and central Americas
Frugiverous and herbivores
Means they can see color
Color vision develops here (Is this fruit ripe? Edible? Nutritious?)
Females have trichromatic; Males have Dichromatic
Color vision is located on the X chromosome on these species.
General characteristics of Ceropithecoids
OCCUPY LESS TROPICAL HABITATS AND DON’T ALWAYS SPEND TIME IN TREES---SO THEY’RE MORE LIKE US!
African and Asian monkeys (old world monkeys)
Across wide variety of habitats. Many quadripedally moving
More geographically widespread
Trichromatic color vision
General characteristics of Hominoidea
All exhibit some form of bipedalism
Slower life histories - they have longer generational span and live longer
Many at risk of extinction - due to fragmentation and habitat destruction.
Where did color vision evolve and why
Color vision developed in Platyrrhini due to being frugivores (need to be able to detect safe fruits.)
General characteristics of early hominins
Hominins are mostly extinct species that are more closely related to humans than to chimpanzees
Early hominins shared derived traits with humans
Reduced canine teeth
Relatively flat faces
Increasingly upright and bipedal
Hominin, any member of the zoological “tribe”(The tribe level occurs between the subfamily and genus.) Hominini (family Hominidae, order Primates), of which only one species exists today—Homo sapiens, or human beings. The term is used most often to refer to extinct members of the human lineage, some of which are now quite well known from fossil remains
The main difference between hominid and hominin is that hominid is the family to which humans belong whereas hominin is the tribe level to which humans belong to.
Relatively small animals.
Who were the Australopiths?
Australopiths are a paraphyletic assemblage of hominins that lived 4–2 million years ago
Australopithecus anamensis (4.2–3.9 million years ago) is the earliest known australopith
A. africanus (3–2.4 million years ago) walked fully erect and had humanlike hands and teeth
A. afarensis (3.2–2.2 million years ago) was fully bipedal, had a small brain and body, and a long lower jaw
Paraphyletic - (of a group of organisms) descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups.
Bipedal walking was energy efficient in the arid environments inhabited by hominins at the time
Oldest representatives are 4-2 million years ago
Beginnings of walking fully erect
1.9 million years ago – arid, dry climates; it’s a desert and there aren’t a lot of resources. I need to be able to migrate out and find food.
Only two parts of my body touch the ground. See larger distances and find where food is.
Time when climatic variables are forcing hominins to be more efficient movers.
Characteristics of the genus Homo
Sexual dimorphism (size difference between sexes) decreased in H. ergaster and later Homo species
Reduced sexual dimorphism is associated with species that undergo more pair-bonding
H. habilis Tools become an important part of evolution. Associated with brains and mouth structure, there is evidence of the tools driving evolution
Homo eragaster is fully bipedal, large-brained homonins. Long slender legs with hip joints well adapted for long-distance walking. Their teeth were smaller than austalopiths, adapted for eating softer foods
General characteristics of humans
Homo sapiens arose about 200,000 years ago. Several Homo species alive. Evolving in different places. H. sapiens evolved somewhere around Africa.
upright posture and bipedal locomotion
Larger brains (capable of language, symbolic thought, and artistic expression)
Production and use of tools (we have discovered considerably more about how to make
tools than any other species) How to make metal out of rocks.
Reduced jawbones and jaw muscles (extremely small bite structure and bite force).
Shorter digestive tract. (less crude foods)
How do humans fit in the phylogenetic tree?
Homo sapiens → hominins → hominoids → primates → supraprimates → eutherians → mammals → synapsids → amniotes → tetrapods → lobed-fin fish → bony fish → gnathostomes → vertebrates → chordates → deuterostomes → triploblasts → bilaterians → eumetazoans → metazoans → animals → eukaryotes (Unikonta) → Living things!
Note 
Flashcard (33)