Classifying biology Question: Which is the most similar? -classify by - - PowerPoint PPT Presentation

Classifying biology

Question: Which is the most similar?

• classify by looking at evolutionary relationships

Answer: croc and pigeon

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Macroevolution

Classification: categorize organisms to understand evolutionary relationships Kingdom: Animalia Phyla: Chordata Class: Mammalia Order: Primate Family: Hominidae Genus: Homo Species: sapiens

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Homologies

Homologous traits: similarities due to common descent E.g., birds, bats, mice, crocs all have four limbs Contrast with analogies: similarities due to common function

Classifying biology

Homologies: similarities based on a common ancestor vs Analogies: similarities due to common function

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Two types of homologies

Ancestral traits: similarities in many taxonomic groups inherited from a remote ancestor Derived traits: have been modified from the ancestral conditions

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Homologies some more

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Schools of classification

Evolutionary systematics: hypothesizes about ancestor-descendant relationships over time

• use phylogenetic trees

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Schools of classification

Cladistics: use shared derived traits to identify new species Clades: lineages sharing a common ancestor

• Anthropologists mostly use cladistics

Evolutionary Systematics: explains ancestor-descendant relationships over time Cladistics: uses shared derived traits to classify new species

• no time

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Compare and contrast classification systems

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Generalized vs specialized traits

Generalized traits adapted for many functions Specialized traits arise during adaptive radiation -generalists specialize to niches

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Macroevolutionary processes

Adaptive radiation: rapid expansion and diversification of groups into empty ecological niches Niche: a species place in an environmental setting

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Species concepts

Biological species concept: groups of interbreeding individuals that are reproductively isolated Speciation occurs if

• geographic, behavioral, anatomical isolation
• natural selection is acting on populations
• highly differential niches

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Species concepts

Paleospecies: groups of fossil organisms that are assigned to the same species. Variation over time needs to be considered when classifying paleospecies Intraspecific: variation within species Interspecific: variation between species

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Fossils: remains of organisms preserved over time

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Fossils: remains of organisms preserved over time

*Mineralization: organic material chemically turned into rock

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Fossils: remains of organisms preserved over time

*Mineralization: organic material chemically turned into rock *Organisms are trapped in tree resin/an anoxic environment

*Mineralization: organic material chemically turned into rock *Organisms are trapped in tree resin/an anoxic environment *Imprints of tracks or leaves in hardened mud

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Fossils: remains of organisms preserved over time

Video question

Attendance: Write your name on a piece of paper and respond to the following question: Identify at least three examples of the different concepts discussed in the course so far. E.g., Homologies, mitosis, meiosis, natural selection, selective pressures, genetic drift, gene flow (migration), mutation, etc. https://youtu.be/StqZI9pMq0U

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Paleozoic era (570-225 mya)

• first vertebrates emerged
• first mammal-like reptiles
• Pangaea formed

Mesozoic era (225-65 mya)

• Age of dinosaurs

Cenozoic era (65-0 mya)

• Age of mammals

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Continental drift: movement of continents on Earth's surface

• causes mountain building, volcanic activity, earthquakes, etc

Late Paleozoic to Late Mesozoic

• plate tectonics caused reproductive isolation

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Mesozoic to Cenozoic

Late Mesozoic era: Age of Dinosaurs

• earliest mammals

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Cenozoic era: age of the mammals

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Mesozoic to Cenozoic

Late Mesozoic era: Age of Dinosaurs

• earliest mammals

Cenozoic era: age of the mammals

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Three modern mammalian subgroups

Monotremes: most ancestral mammals, e.g., they lay eggs

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Three modern mammalian subgroups

Marsupials: immature birth; development continued in pouch

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Three modern mammalian subgroups

Placental: in utero development

Paleozoic era (570-225 mya)

• first vertebrates emerged
• first mammal-like reptiles
• Pangaea formed

Mesozoic era (225-65 mya)

• Age of dinosaurs

Cenozoic era (65-0 mya)

• Age of mammals

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Mammalian shared derived homologies

• Endothermic
• Heterodont dentition
• Placental
• Complex brains and

flexible behavior