Phylogeny 3 Flashcards
how big is the tree of life
- very big: almost any species has a vast and dense phylogenetic neighbourhood
how many species are currently described in the tree of life
- about 2 million species
systematics (2)
- field that reconstructs phylogenetic relationships
- we have a good idea of the broad phylogenetic relationships of species we have discovered, but most species are still unknown
how well do we know the leaves of the Tree of Life (2)
- not very well as most species on Earth are still undiscovered, and even the ones we have discovered have not been studied intensely
- we should expect at least 20 million species on Earth, meaning we have only discovered 10% or fewer of the species on Earth
how well do we know the tree of life in general
- reasonably well in broad structure, but the details are poorly known in most subgroups and most species remain to be discovered
arthropods
- include insects, spiders, and crustaceans
echinoderms
- include sea stars, sea urchins, sea cucumbers
nucleus and sex
- characteristic of all eukaryotes
muscle cells
- characteristic of all animals
head
- characteristic of all animals, except for jellyfish & corals
skeleton with backbone
- characteristic of all vertebrates
legs
- characteristic of all tetrapods
eukaryotes (6)
- animals, plants, fungi, algae, ciliates, and other protists
what is red algae close to
- green algae
what is fungi close to
- animals
what are ciliates close to
- brown algae
what is archaea the sister group to
- eukaryotes
what is bacteria the sister group to
- all the rest of life
how characteristics can we use to memorize plant phylogeny (3)
- on land: mosses, ferns, conifers, flowering plants
- vascular system: ferns, conifers, flowering plants
- seeds: conifers, flowering plants
which animals lack a head
- jellyfish and corals
which clades are close and share spiral cleavage in animal phylogeny
- molluscs (snails, squids, clams), arthropods, and nematodes
what are echinoderms close to
- vertebrates
within vertebrates, which clades are not included within tetrapods (3)
- fish (have fins and not legs): sharks, rayfinned fishes, and lungfish
what are frogs and salamanders the sister group to
- amniotes
what are mammals the sister group to
- lizards & snakes, birds, and turtles
why are model organisms used to understand humans
- they are an attempt to reconstruct the traits of our ancestors
what is the time scale of evolution
- millions of years; depicted by the “geological time scale”
what are the major stages of the “geological time scale” (4)
- precambrian (4600 - 540)
- paleozoic (540 - 252)
- mesozoic (252 - 66)
- cenozoic (66 - 0)
precambrian era
- mostly single-celled organisms and not much on land
what were the main events of the precambrian era (4)
- origin of earth (4.6 mya)
- origin of life (4 bya)
- oxygenation catastrophe (2.4 bya)
- origin of multi-cellular animals (0.7 - 1 bya)
the oxygenations catastrophe (3)
- life’s first major environmental disaster
- the anaerobic world flipped to primarily aerobic because of photosynthesis producing oxygen
- 2.4 bya
what was the major event of the late precambrian era
- multicellular animals appearing
what were the major events of the paleozoic era (2)
- cambrian explosion
- plants & animals on land; first tetrapods
cambrian explosion
- early paleozoic era
- marine animal fossils suddenly became abundant: arthropods, chordates, molluscs all present
what is characteristic of the mid-late paleozoic era
- abundant life on land due to the appearance of tetrapods 395 mya
what is the main event of the mesozoic era
- origin of dinosaurs and mammals
what is the main event of the cenozoic era
- the origin of hominids where primates evolved
how deep is the tree of life
- 3-4 billion years deep, but diversification of familiar multicellular organisms happened mostly in the last 600 millions years
how do we treat fossils when studying phylogeny
- we link fossils through strata to explain morphological changes most simply; we end up treating fossils like living species
