Bio 1101 Lecture 14- How Biological Diversity Evolves PDF

10/24/2024 Random Animal of the Week! Hickory Horned Devil, the caterpillar...

10/24/2024 Random Animal of the Week! Hickory Horned Devil, the caterpillar of the Regal Moth (Citheronia regalis) Bio 1101 Lecture 14 Found across much of eastern US Chapter 14: How Biological Caterpillars feed on leaves of hickory, walnut and pecan trees; adults do not eat Diversity Evolves Moths lay their eggs on leaves of trees; larvae hatch, feed, and grow, molting four times The final instar burrows into the ground to pupate overwinter They metamorphose into the beautiful Regal Moth, which only lives for one or two weeks 1 2 Chapter 14: How Biological Diversity Evolves Microevolution = the generation-to-generation change in a population’s frequencies of alleles Range is across much of eastern US Macroevolution = major biological changes, including the formation of new species Largest caterpillar in North America! Caterpillars are so large, often How did the diversity of species on earth arise? compared to hotdogs! 3 4 Branching evolution is responsible for the multiplication of species But what is a species? Biological Species Concept: groups of interbreeding natural populations that are reproductively isolated from other such groups What keeps closely related species from interbreeding? 5 6 1  10/24/2024 Pre-zygotic isolating mechanisms – Prevent the formation of a zygote Temporal isolation Geographic isolation Behavioral isolation Mechanical isolation Gametic isolation 7 8 Post-zygotic isolation – Prevents hybrid offspring Allopatric Speciation from developing or reproducing – A geographic barrier divides a population, Hybrid inviability preventing gene flow Hybrid sterility – Example 1: A river flowing through a population – Male lion and female tiger → eventually carves a canyon in the middle of the liger – Male tiger and female lion → population, isolating the individuals on either side. tigon (2 different species of squirrel on either side of – Male donkey & female horse → Grand Canyon) mule – Example 2: During a storm, some individuals get blown off a mainland onto an island and are then isolated from the mainland population 9 10 Islands offer excellent examples of how new species can arise when isolated from their parent populations – Example: Galapagos finches; beak shape adapted for food sources on different islands 11 12 2  10/24/2024 – Genetic isolation of two populations may or may not result in speciation Sympatric Speciation Speciation requires the evolution of reproductive – The origin of new species without geographic barriers between the isolated population and its parent isolation population – Not common among animals, but fairly common in plants – Often a result of a genetic mutation that results in the formation of a new species in one generation – Usually from an accident during cell division resulting in an extra set of chromosomes, called polyploidy; the increased number of chromosomes makes the individual reproductively incompatible with the parent species 13 14 – Examples of polyploid species: the gray treefrog and the Chinese hibiscus 15 16 Punctuated Equilibrium – Most species-defining characteristics change over What is the tempo of speciation? a relatively short period of time in the overall lifetime for that particular species – Most species will live a few million years… but 2 Concepts: Gradualism and Punctuated only a few thousand of those years may be Equilibrium involved in the physical evolution of that species – Change occurs in relatively short “bursts,” followed by long periods of stasis Gradualism: continuous, slow accumulation – Likely a better fit to the way species actually of changes over a very, very, very long period evolve of time 17 18 3  10/24/2024 – Species evolve in response to changes in Organisms are Classified based on their environment Evolutionary Relationships – Our taxonomic system was developed by Carolus Linnaeus in the mid-1700s – “Binomial nomenclature” – a two-part scientific name for each species The Genus name The Specific Epithet Both parts are written in italics; the genus name is capitalized Examples: Homo sapiens = modern humans; Rana pipiens = leopard frog; Rana sylvatica = wood frog 19 20 Taxonomy Organisms are organized into a hierarchical classification system Arum maculatum vs – Domain Ambystoma maculatum – Kingdom – Phylum – Class – Order – Family – Genus – Species 21 22 Organisms are classified into these groups based on their characteristics – Organisms that share homologous structures (derived from a common ancestor) – The more homologous characters they share, the more closely related they are 23 24 4  10/24/2024 The Geological Time Scale A History of the Earth (Table 14.1) – Earth was formed approximately 4.6 BYA – 3.5 BYA – first prokaryotes – 2.7 BYA – oxygen began accumulating – 2.2 BYA – oldest eukaryotes – 700 MYA – oldest animal fossils – 600 MYA – invertebrates diversify; algae diversify 25 26 – ~540 MYA – the Cambrian Explosion; most Plate Tectonics and Biogeography modern animal phyla evolved – The continents and seafloors form a thin layer of rock – ~500 MYA – origin of true plants called the crust, which moves over a mass of hot, – See Table 14.1 viscous material called the mantle First vertebrates, the fishes evolved about 430 MYA – The crust is not one continuous piece, but is divided By 300 MYA, there were extensive land forests, into giant, irregularly shaped plates that move amphibians were the dominant land animals, and – Where plates touch, there is geologic activity such as reptiles originated volcanos, mountain uplift, and earthquakes when the About 65 MYA, dinosaurs went extinct, and flowering plates scrape past each other and collide plants evolved; this was followed by diversification of mammals, birds, and pollinating insects – About 250 million years ago, plate movements caused all of the previously separated land masses to come First Homo sapiens were the Neanderthals, about together and form a supercontinent called Pangea 130,000 years ago – Movement of plates is slow, but over the course of history they have moved thousands of miles 27 28 Biogeography: the study of past and present distribution of organisms – The formation of Pangea must have had dramatic impacts on species that had formerly been isolated – When Pangea broke up during the mid-Mesozoic era, the separation of once-contiguous land masses and populations once again forced species to adapt to new conditions Example of Madagascar (large island off the southern coast of Africa) – nearly all animals and plants here are unique, having diversified from ancestral populations when the island broke away from Africa and India – More than 50 species of lemurs, which evolved from a common ancestor over the past 40 million years Video: Bill Nye Tectonic Plates - YouTube 29 30 5  10/24/2024 Continental drift also separated Australia from other landmasses – Australia and its adjacent islands are home to over 200 species of marsupials (most found nowhere else in world – they are “endemic”) – Most other parts of the world are dominated by placental mammals; why so few marsupials? – Distribution of marsupials makes sense in light of continental drift-- marsupials must have originated when the continents were joined Fossil evidence indicates they originated in what is now Asia, later dispersing to South America while it was still connected to Antarctica; they made their way to Australia before continental drift broke apart Pangea The marsupials in Australia thrived, while placental mammals did better in other landmasses 31 32 Mechanisms of Macroevolution Scientists working at the interface of evolutionary biology and developmental biology, – the research field abbreviated evo-devo, – are studying how slight genetic changes can become magnified into major structural differences between species. 33 34 Changes in rate of developmental events Homeotic genes, the master control genes, explain changes in the homologous limb program development by controlling changes bones of vertebrates. in an organism’s form as it develops from a – Increased growth rates produced the extra-long zygote into an adult, affecting the “finger” bones in bat wings. – rate, – Slower growth rates of leg and pelvic bones led to – timing, and the eventual loss of hind limbs in whales. – spatial pattern of organisms 35 36 6  10/24/2024 Paedomorphosis – is the retention in the adult of body structures that were juvenile features in an ancestral species and – has occurred in the evolution of axolotl salamanders humans 37 38 – In human evolution, Structure/Function: Adaptation of Old genetic changes slowed the growth Structures for New Functions of the jaw relative to other parts of the skull and produced The feathered flight of birds is a perfect an adult with head marriage of structure and function. proportions similar to a child – This resulted in In flight, the shapes and arrangements of larger brain case various feathers and bigger brain (growth of brain – produce lift, switched off later than in – smooth airflow, and chimpanzees), so our brains grow for – help with steering and balance. several more years – a prolonged juvenile process 39 40 How did such a Thousands of fossils of feathered dinosaurs have been found and classified into more than 30 beautifully intricate different species. structure evolve? But the feathers seen in these fossils could not Reptilian features have been used for flight, nor would their reptilian anatomy have been suited to flying. apparent in fossils of Their first utility may have been for insulation. Archaeopteryx, one Once flight itself became an advantage, natural of the earliest birds, selection would have gradually remodeled offered clues in feathers and wings to fit their additional function. Darwin’s time. Structures such as feathers that evolve in one context but become co-opted for another function are called exaptations. 41 42 7  10/24/2024 From Simple to Complex Structures in Gradual Stages Patch of Eyecup Simple Eye with Complex camera pigmented cells pinhole eye primitive lens lens-type eye Most complex structures have evolved in small Pigmented cells (photoreceptors) Pigmented cells Fluid-filled cavity Transparent protective tissue (cornea) Cornea steps from simpler versions having the same Lens Lens basic function, a process of refinement rather than the sudden appearance of complexity. Eyecup Retina Layer of Retina The evolution of complex eyes can be traced Nerve Nerve Optic Optic Optic fibers fibers nerve pigmented nerve nerve cells (retina) from a simple ancestral patch of photoreceptor cells through a series of incremental modifications that benefited their owners at each stage. Limpet Abalone Nautilus Marine snail Squid 43 44 Frequently a difficult concept to grasp – how All for today something as complex as an eye could evolve – but step by step, small genetic changes can result in increasingly complex organs for perceiving light information Video: https://www.youtube.com/watch?v=dWFteFf g2J0 45 46 8