Lesson 24 - Reptiles Birds & Mammals

24: reptiles, birds, & mammals Monday, March 25, 2024 12:55 PM relative to other extinct species that pre-date tetrapods, what traits make Tiktaalik a transitional species? a. bones in fins b. lobe fins ○ group prior (lungfish, coelacanths) c. lived on land ○ ability to crawl onto land but not live on land d. all of the above derived traits of amniotes • • • • amniotic egg with four membranes eggs with shells or internal gestation ○ gestation: in womb ○ two methods of reducing water loss of developing embryo less permeable skin ○ reduced water loss of adults ○ shown differently in different species ○ skin is no longer a respiratory organ in amniotes rib cage used for ventilation ○ efficient gas exchange ○ improves lung function ○ lungs are only method of gas exchange ○ skin is no longer permeable phylogeny of amniotes • • • • • tetrapods and chordates turtles and reptilians are more basal than crocodiles and birds birds are within the clade of dinosaurs ○ they are reptiles and dinosaurs ○ avian dinosaurs squamates: lizards and snakes reptiles have two clades amniotes: reptiles • • • • • scales/feathers containing keratin ○ prevent desiccation (water loss) ○ keratin strengthens the integumentary organs; similar to chitin all amniotes and have amniotic eggs lay shelled eggs on land ○ internal fertilization is followed by shell secretion ○ includes marine reptiles, such as sea turtles § have to move to land to lay eggs snakes/lizards are ectotherms ○ regulate temperature with behavior ○ ex. basking in the sun birds are endotherms ○ internal temperature regulation ○ derived trait ○ mammals are also endotherms § convergence between birds and mammals turtles (reptiles) • • 307 species upper and lower shells fused to vertebrae, collarbones, and ribs ○ mammals are also endotherms § convergence between birds and mammals turtles (reptiles) • • • • 307 species upper and lower shells fused to vertebrae, collarbones, and ribs found in many different habitats: ○ on land, in ponds, rivers, and oceans divided into two groups based on neck retraction squamates: lizards & snakes • • • 9,000 species (larger/more diverse group among vertebrates) lizards: ○ from a few cm to > 3 m ○ many examples of convergence, including loss of limbs and climbing smooth surfaces ○ demonstrates local adaptation and evolution, especially on islands snakes: ○ squarely in the squamate group; a type of lizard ○ ancestors were burrowing or aquatic lizards who lost limbs ○ many vestigial structures (ex. pelvis) ○ carnivores with adaptations hunting and capturing prey § venom § camouflage § unhinged jaws § strong sense of smell; chemoreceptors § heat sensors for mammalian prey birds • • • • 10,000 species ○ largest group of amniotes ○ might be as many as 18,000 ○ new species vs. subspecies evolved from dinosaurs 160 MYA diversification occurred 66 MYA ○ fifth mass extinction ○ when non-avian dinosaurs disappeared, giving an opportunity for avian explosion modifications for flight ○ strength to lift off the ground and lightness to remain in the air ○ hollow/honeycombed bones ○ reduced organs (no bladder, one ovary, small gonads) ○ no teeth § a loss § possessed by non-avian dinosaurs feathers ○ ○ large pectoral muscles researchers suspect that early ancestors of birds were flightless but had feathers. what have researchers inferred from this observation? ○ ○ § a loss § possessed by non-avian dinosaurs feathers large pectoral muscles researchers suspect that early ancestors of birds were flightless but had feathers. what have researchers inferred from this observation? a. early feathers were not aerodynamic, limiting flight b. early birds were too heavy to fly, even if they tried c. early birds had not yet learned the mechanics of flight, so they couldn't use their feathers d. feathers initially evolved for another function which of the following is a derived trait exclusive to mammals? a. hair b. parental care ○ birds, insects, arachnids, frogs, etc. ○ extended in mammals c. ability to learn ○ birds, cephalopods, etc. d. all of the above derived traits of mammals • • mammary glands ○ milk secretion endotherms hair ○ homologous trait that can be lost ○ insulation needed as endotherms fat layer under skin • • ○ insulation larger brains extended parental care • • • • • • • ○ insulation needed as endotherms fat layer under skin ○ insulation larger brains extended parental care ○ beyond birth and during gestation/incubation diverse teeth ○ reptiles have more uniform teeth shapes ○ different functions: grinding, tearing, grasping ○ helps to diversify their diet 5,400 species (< 10% of vertebrates) ○ 5,000 are eutherians evolution of mammals • • • • • animals with mammal-like traits appear 300 MYA true mammals appeared 200 - 145 MYA ○ based on defining characteristics co-occurred with dinosaurs 3 major lineages arose 140 MYA ○ monotremes, marsupials, and eutherians ○ not much mammal diversity adaptive radiation at the end of the cretaceous (66 MYA) ○ diversification occurred ○ when non-avian dinosaurs (dinosaurs) disappeared ○ currently the dominant class of vertebrates mammals: monotremes and marsupials • • • more basal groups monotremes: platypus, echidna ○ 5 species ○ lay eggs § not typical in mammals § transitional species; also similar to reptiles ○ have mammary glands but lack nipples § mammary glands make them categorized as mammals § leak milk onto stomach marsupials: opossums, kangaroos, koalas ○ ~ 300 species ○ possesses a pouch § transitional structure ○ no eggs - early development in uterus, includes a simple placenta ○ an incomplete embryo is born; underdeveloped ○ complete embryonic development outside uterus (in pouch/incubator) while nursing eutherians (placental mammals) • • largest group of mammals placental animals have a placenta, but some animals have a placenta but are not ○ complete embryonic development outside uterus (in pouch/incubator) while nursing eutherians (placental mammals) • • • • • • • largest group of mammals placental animals have a placenta, but some animals have a placenta but are not considered a placental organism more complex placentas (than marsupials) development completely in uterus lack epipubic bone ○ allows expansion of uterus/abdomen during pregnancy longer pregnancy ○ african elephants gestate for 645 days divergence of groups fuzzy ○ between 100 - 60 MYA primates • • • 190 - 448 species depending on classification system arose 85 - 55 million years name means "first-ranked" ○ linnaeus saw primates as the highest order of animals derived traits of primates • • • • • hands and feet adapted for grasping ○ not just motility flat nails instead of claws large brains, short jaws ○ complex thought, shift in diet eyes look forward - hand/eye coordination ○ not unique to primates, but the function is monkeys/apes only: flexible or opposable thumbs ○ anthropoids ○ not in basal primates ○ easier to grasp objects primate lineages • • apes diverged from old world monkeys 25 - 30 MYA non-human apes now found only in old world tropics based on the tree, which of the following is true? a. apes diverged from old world monkeys ○ shared a common ancestor b. apes are a paraphyletic clade ○ there is no such thing as a paraphyletic clade § paraphyletic: single common ancestor but does not include all descendants from the ancestor ○ clades are monophyletic c. humans evolved from chimpanzees ○ they are a sister taxa/clade ○ evolve from a common ancestor, closely related d. all of the above which of the following statements is true? a. all mammals have live births ○ not monotremes b. all eutherians have maternal care c. all primates have opposable thumbs ○ not basal primates (lemurs, bushbabies, etc.) ○ only monkeys and apes d. all of the above derived traits of hominins • • • • includes every species in the genus Homo and close (human) relatives upright and bipedal ○ working toward this particular phenotype larger brain, complex thought, tool use ○ relative to other primates and most mammals in terms of body size ○ more neural connections and synapses ○ complex thought: the ability to demonstrate logic and response-reaction time ○ other groups use tools (ex. birds using rocks to obtain food) reduced jawbones and teeth • • • ○ working toward this particular phenotype larger brain, complex thought, tool use ○ relative to other primates and most mammals in terms of body size ○ more neural connections and synapses ○ complex thought: the ability to demonstrate logic and response-reaction time ○ other groups use tools (ex. birds using rocks to obtain food) reduced jawbones and teeth ○ associated with diverse changes in diet shorter digestive tract ○ changes in diet hominin evolution • • excludes groups that were more recently discovered little is known about our own evolution early hominins • • 6.5 MYA - evidence of first hominins ○ reliant on the fossil record ○ more upright than other apes ○ reduced canine teeth ○ shifts in phenotype australopiths date to 4-2 MYA ○ ○ ○ lucy: the first semi-complete skeleton of australopiths discovered walked fully erect human-like hands and feet • ○ reduced canine teeth ○ shifts in phenotype australopiths date to 4-2 MYA ○ ○ ○ ○ ○ ○ lucy: the first semi-complete skeleton of australopiths discovered walked fully erect human-like hands and feet could still choose to walk on all fours, but had the ability to walk fully upright human-like hands and feet first human resembling hominin hominins: early Homo • • Homo erectus (1.8 - 0.2 MYA) ○ long evolutionary footprint § may have persisted into more recent times more human resembling ○ ○ taller (5-6 feet) ○ social adaptations: used fire to cook food ○ first group in the genus Homo to migrate out of africa to europe/a different habitat ○ first ancient hominin to be discovered, explaining the name "erectus" when australopiths walked upright beforehand Homo neanderthalensis (4000,000 - 40,000 YA) ○ did not originate in africa, their common ancestors did ○ evolved and lived in europe and asia § cooler climate ○ short, stocky bodies adapted to the cold ○ share a common ancestor with humans (Homo sapiens); closest sister taxa within hominins hominins: Homo sapiens • • • • • • originated in africa around 200,000 years ago (might be older) lighter skeletons ○ smaller frame and bones overall "modern" skull is thin-walled with a vertical forehead ○ shift in brow and weight of skull smaller teeth hunting and fishing with specialized tools ○ able to modify tools developed sophisticated societies and culture practices ○ thought to have been done previously, such as by Homo neanderthalensis ○ advanced by Homo sapiens dispersal of Homo sapiens • • ancestor of all humans originated from africa ~200,000 years ago (strong evidence) evolved as its own species (200,000 - 300,000 YA) • • migrated to the middle east (100,000 YA) from the middle east to europe, asia, and australia (70,000 YA) ○ old world (plus africa) • • ancestor of all humans originated from africa ~200,000 years ago (strong evidence) evolved as its own species (200,000 - 300,000 YA) • • migrated to the middle east (100,000 YA) from the middle east to europe, asia, and australia (70,000 YA) ○ old world (plus africa) from asia to the americas (15,000 YA) ○ new world • why are we the only hominins? • • • • • • other genera have many species, such as other primates and animals we are the only existing species of the genus early Homo sapiens coexisted with other Homo species (at least two) ○ interbreeding occurred between several groups ○ europeans could have neanderthal dna changes in lifestyle around 50,000 years ago led Homo sapiens to replace other species hypothesized that we outcompeted other species ○ more advanced tools ○ elaborate shelters ○ social, cultural development § increased fitness (ex. methods of child rearing and foraging) most successful species which of the following statements about hominins is true? a. all species in the genus Homo lived in africa ○ neanderthalis resided in europe and asia b. Homo sapiens originated in africa c. the genus Homo represents the first hominins to walk fully upright ○ lucy (an australopith) was the first d. when Homo sapiens evolved, they immediate replaced all other hominin species ○ known to coexist with other hominins