Origins and Patterns of Biodiversity: BIOS 120

complicated mutualism examples

neotropical orchid bees, flowers of the Theobroma tree, a poison-dart frog

ecological species concept

- "Species are Groups of Organisms that Share Certain Traits" that have been shaped by natural selection to fill a distinct niche - If sexually reproducing must be actually or potentially interbreeding - Must be a discrete lineage recognizably different from other such lineages and with a distinct evolutionary history.

Homology

- A character state is homologous in two species when it is inherited by both from a common ancestor. - The most widely accepted school of systematics today is called cladistics. - Cladistics infers the pattern of phylogeny based on homologies. - Groups are constructed based on shared characteristics inherited from a common ancestor, that no other group has. - Trees are constructed by creating a nested series of such groups. - For any group of taxa, a pattern of loss and acquisition of characters, and the subsequent passing-down of these traits to descendent species, can be mapped on a tree called a cladogram. - The cladogram with the fewest number of transitions and reversals (parsimony), or the one with the most likely series of transitions (maximum likelihood), is chosen as the best-supported phylogeny.

Monophyletic groups

- A monophyletic group is all the descendants of a common ancestor. - Polyphyletic groups do not share a common ancestor. - Paraphyletic groups have a common ancestor, but exclude some taxa.

the Tree of Life

- All organisms on Earth descend from a single, common ancestor. - This ancestor may have been a single species, or a cluster of organisms freely exchanging genetic material. - If other, unrelated forms of life existed, they have gone extinct by now...we know this because: - Except for a few viruses, which may have undergone retrograde evolution, all forms of life on Earth use DNA as the genetic material. - All forms of life share a common, virtually-identical genetic code. - All forms of life rely on the same biomolecules-amino acids, sugars, etc.

Genetic Diversity example in plants

- An example of biodiversity that includes genetic diversity within a species is varieties of cultivated plants. - The tomato, Solanum lycopersicum, is a single species of plant, originally from the Andes. - There are over 7500 varieties of tomatoes, each with its own characteristic allele pool. - These include hundreds of heirloom varieties.

reproductive isolation

- At the time when a genetic or behavioral mechanism evolves that keeps populations of a species from interbreeding, these two species become reproductively isolated. - If this reproductive isolation continues long enough, speciation occurs. One, or several, new species originate from isolated populations of the parent species. - As we shall see, this is frequently the result of a geographic barrier, although it may be the result of a chromosomal change or habitat preference.

isolation mechanism

- Barriers to allele flow are called isolation mechanisms. - Isolation mechanisms allow sympatric species to exist and to maintain distinct sets of characters and adaptations. - Without isolation mechanisms, closely related species would hybridize: allele flow and recombination would eventually transform them into a single, polymorphic species. - Isolation mechanisms are responsible for the origin of species, and they maintain the integrity of species over evolutionary time.

higher level taxonomic biodiversity

- Deep divisions on the tree of life represent biodiversity as well. - There is some evidence that, for animals, the number of higher level taxa (phyla and maybe classes) has decreased over time, since their origins 500 million years ago, but the number of species has increased significantly. EXAMPLE: Biodiversity of marine families over time

taxonomic diversity

- Every ecosystem, habitat, or location can, at least hypothetically, be assessed for the number of different species it contains. - In practice-this assessment depends a great deal on 1) who is looking, 2) how much effort and how long the look, and 3) what lineages the observer expects to see or is interested in counting. A herpetologist can get a very good measurement of how many lizards are living on an island in just a few days, but a botanist might need weeks or months to produce an estimate of ALPHA DIVERSITY for the island, because identification of plants often depends upon flowers or structures that are seasonal in occurrence - Do escaped pets count as local taxonomic diversity? What if they have established populations? EXAMPLE: feral goldfish

Ecological Niches Determine Local Biodiversity

- Every species in an environment must occupy its own, unique, ecological niche. - The availability of ecological niches is determined by community structure.

Evolutionary Convergence, or Convergent Evolution

- Evolutionary Convergence, or Convergent Evolution reflects different species' adaptations to a similar environmental challenge. - In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. EXAMPLE: Horned Viper (Middle East) and Sidewinder rattlesnake (North American deserts)

Factors Determining the Geographic Range of a Species

- History - Biological Tolerances - Other Species - A combination of the above

Hybridization

- Hybridization between animal species occurs in nature, though the products of such events are not usually considered to be species in their own right because they are generally sterile. - Female, hybrids arise every generation from the two parent species. Offspring of these females are malformed and have zero fitness.

Homoplasy

- If a character has evolved more than once, if possessed by two species but not present in the common ancestor, it is called a homoplasy. - One form of homoplasy is called convergent evolution, it is quite common because different species are often subject to similar selective pressures. - Homoplasy, when mistaken for homology, can obscure the pattern of evolutionary history.

extinction of many animals weighing more than 40kg

- In North America around 33 of 45 genera of large mammals became extinct. - In South America 46 of 58 - In Australia 15 of 16 - In Europe 7 of 23 - In Subsaharan Africa only 2 of 44 - In Polynesia, all the moas in New Zealand went extinct shortly after the arrival of humans. - Madagascar saw an extinction of large lemurs and other creatures shortly after the arrival of humans.

community and ecosystem diversity

- Living things are organized into communities and ecosystems. The loss of these units represents substantial loss of biodiversity, even if the species still exist in captivity. - Some communities might even result from human cultural practices. For instance, in Great Britain, pastures grazed using traditional methods represent an important conservation issue. They harbor a unique assemblage of organisms from their long interaction with humans. EXAMPLE: Yorkshire dales

Gondwana Distribution

- Many species have what is called a "Gondwanan" distribution. - They occur in the Southern continents of Australia, South Africa, South America, and sometimes India. - These places are far away from each other now, but 150 million years ago, they were all linked together in a massive continent. - Examples number in the thousands, across many different types of species, including the rattite birds, the bee family colettidae, and the southern beech tree, Nothofagus sp.

Quaternary Extinction of Megafauna

- Mass extinctions often occur in "pulses". - For example, the Permian-Triassic extinction was likely a combination of two severe mass extinctions, one from volcanism, one from a destabilized ocean. - The first "pulse" of the current mass extinction seems to have already happened. - Scientists have not reached a consensus, but it seems likely that humans played a role in the extinction of many large megafauna in Asia, North America, Polynesia, Australia, and other places, over the last few thousand years. The extinctions occur in the immediate wake of the arrival of humans.

The Cretaceous-Paleogene Mass Extinction

- One of the best-understood mass-extinctions occurred at the end of the Mesozoic era, at the boundary between the Cretaceous Period and the Neogene period. - Every species of non-avian dinosaur was driven extinct, as well as pterosaurs, mosasaurs, plesiosaurs, the ammonoid and belemnoid molluscs, rudist bivalves, and quite a few other taxa as well. - Approximately 50% of species on the planet were eliminated, over an interval of a few thousand years. - The scientific consensus, at the moment, is that one or several impact events are responsible for the extinction-though a severe marine regression at the time, and climate change induced by a period of intense vulcanism, may have played a role, rendering the biosphere much more susceptible to mass extinctions resulting from an impact.

Polyploidy in plants

- Polyploidy is more common in plants - Plants are frequently capable of self-fertilization, and some can survive with double the normal number of chromosomes, and most can propogate asexually. - Plants have no real germ line-somatic tissue can give rise to meiotic tissue under a variety of circumstances-thus, an asexual species is likely to have individuals that have spontaneously doubled their chromosome number, and are forming gametes. - Many common agricultural plants are the products of one, or both of the mechanisms above.

polyploidy in the apple maggot

- Polyploidy: allopolyploidy and autopolyploidy - Nonrandom mating: I.e., host shift - the apple maggot- a species that has originated via host shift. When apples were introduced to North America, a shift to apple hosts promoted sympatric speciation.

The Human Mass-Extinction

- Since the development of agriculture, 10,000 years ago, humans have modified an increasing proportion of the Earth's resources for our own purposes. - Humans impact has caused extinction rates to be 10 to 1000 times greater than any time in the last 100,000 years. - For example-one estimate for the recent background extinction rate for birds is one species extinction per 400 years. - If only this natural rate of loss affected the number of bird species, no more than a couple of extinctions should have occurred in the past 800 years. - Scientists estimate that the actual loss during this time period lies somewhere between 200 and 2,000. - We have set in motion a mass extinction, one of the largest, that will not culminate until thousands of years from now.

speciation

- Speciation is the origin of new species. With extinction, it is one of two keystone processes of macroevolution - It is one of two cornerstone processes of macroevolution. - Ironically, Darwin was wrong about the origin of species. He assumed that, given enough time, natural selection would inevitably produce them. This is not actually the case. It takes reproductive isolation for species to originate.

background extinction rate

- Species go extinct because of normal ecological or evolutionary processes, and as they disappear, other species take their places. - For instance, on oceanic islands, the arrival of a predator, such as a monitor lizard or a snake, might precipitate the extinction of ground-nesting birds. Any such birds that are endemic to the island (that is, they live nowhere else) are gone for good. - But oceanic islands come and go, as geological forces shape the Earth's crust, and such extinctions are considered to be "normal".

sympatric species

- Sympatric species live in the same place. Without some mechanism preventing allele and gene exchange among sympatric species, distinct species would be impossible. - Instead, we would see a continuum of variation from one form of life to another, and many forms of life would not be possible, because interbreeding with different forms would produce non-viable combinations of traits.

synapmorphy and synplesiomorphy

- Synapomorphy-a novel (derived) trait that a group has inherited because the common ancestor of that group had a novel characteristic and passed it on. - Synplesiomorphy-an evolutionarily primitive trait that a group has inherited because the common ancestor of that group had inherited the primitive condition, unchanged, from an earlier group. Note that these terms are relative-a synplesiomorphy for one group may be a synapomorphy from the larger group it came from. EXAMPLE: bee wings, basal veins

hybridization example

- The European edible frog, Pelophylax kl. esculentis, was discovered to be a sterile hybrid between the pool frog P. lessonae and the marsh frog, P. ridibundis. - Note the kl in the species name, indicating it is not a true species.

inferring phylogeny

- The branching pattern that gave rise to a group of taxa can be inferred from a variety of types of evidence. These include: - Morphological, biochemical, behavioral, and genetic features - DNA sequence information-probably the BEST source overall, if it is available, because there is so much of it. - The fossil record - Biogeography - Shared morphological, biochemical, genetic, or behavioral characters that were passed down from a common ancestor called homologies, are the most reliable in constructing a phylogeny for a group of organisms. - Like all hypotheses, they make predictions that can be tested by future study.

Biodiversity

- The concept of biodiversity includes many different ideas regarding the diversity of living things. It encompasses: - The Genetic Diversity within Populations - Diversity of Populations Within Species - Diversity of Species or Lineages (Taxonomic Diversity) - in a given habitat (alpha diversity) - accounting for the diversity of habitats, and the change in --- species from one habitat to the next (beta) - total number of species (gamma) - Communities and Ecosystems

5 Mass Extinctions

- The history of life on Earth has been punctuated by a series of mass-extinctions. - Extinction rates are much higher than background rates for a short period of time. - Some are better understood than others, but they have profoundly influenced the evolution of life on Earth. - Over the last 500 million years, there have been several major mass extinctions (not counting the current one): here are some big ones 1) The Late Devonian 2) Mid-Ordovician 3) Permian-Triassic 4) Late Triassic 5) Cretaceous-Paleogene.

the ocean floor

- The ocean covers 70% of the earth's surface and provides about half the air we breathe, courtesy of the microscopic, oxygen-producing phytoplankton floating in it. - As of the year 2000, the National Oceanic and Atmospheric Administration (NOAA) estimated that as much as 95 percent of thttps://questions.packback.co/loginhe world's oceans are unexplored. - In the 19th century, it was thought that the deep oceans were uninhabitable to living things. This is not true. EXAMPLE: the Challenger expedition was one of the first scientific attempts to explore the deep ocean. - The Census of Marine Life, a decade-long international study of the planet's oceans, uncovered more than 1,200 new species, excluding microbes, since the project began in 2000, and this is a very small fraction of what is out there. EXAMPLE: Abyssal sea cucumber, and carnivorous harps sponge.

How many species are there?

- There are approximately 2 million described species on Earth, true number has been estimated to be 8.7 million, though it may be much higher. - Currently, there are at least 1 million named insect species - There are approximately 53 000 vertebrate species of which approximately 25 000 are fish, 5 000 are mammals, 10,000 are birds, 8,000 are reptiles and 5,000 are amphibians) - There are about 250 000 flowering plant species. - If prokaryote "species" are recognized, the true total can be as many as 100 million.

hybridization exceptions

- There are exceptions, however. Many members of the genus Anas (ducks and teals) are interfertile, and produce fertile hybrids. - In some cases, interspecific hybrids in animals produce asexually reproducing offspring, the asexual lizard, Cnemidopherus neomexicanus (center) is a hybrid between two related species. (C. tigris, right and C. inornatus, left) - Though rare in animals, hybridization does occasional new , sexual, species. The clymene dolphin, Stenella climene is thought to be a result of interspecific hybridization.

phylogenetic species concept

- This concept emphasizes the species as a lineage on the tree of life. - It is, at least in theory, objective, because it defines lineages as the smallest set of organisms that share a common ancestor-though in practice, that common ancestor is always dead, and its existence must be inferred.

biology species concept

- This idea was promoted by Ernst Mayr, an evolutionary biologist who worked on birds. - It is excellent, conceptually, because it defines species objectively, based upon the capabilities of the organisms in question. - In principle, this applies to most species, but in many cases, it is simply impossible to test whether two species have the potential to interbreed. - Fossil species, species which do not reproduce in the lab or zoo (the vast majority), and asexual species are sticky issues.

morphological species concept

- This is what most taxonomists actually use to classify specimens and describe species. - It is expedient-it can be applied to dead specimens, and even to fossils. - It has many disadvantages: It is subjective. Cryptic species, which look identical to humans but are in fact reproductively isolated, are problematic. - Species with morphological variation, and complex life histories, pose problems.

unexplored biodiversity

- Tropical Rainforests; Harbor much of the planet's biodiversity-are becoming increasingly well-understood even as we destroy them. - Ocean Floor; Almost entirely unexplored. - Microbial World; We are just scratching the surface of what is out there.

allopolyploidy example

- Yellow bananas are a sterile allopolyploid, the product of two interspecific hybridization events. - Musa acuminata, one of the sexual species that gave rise to the yellow banana

Adaptive radiation

- a wave of speciation that occurs as a new habitat is colonized by a lineage, in response to the evolution of an evolutionary novelty that allows a lineage to live in a totally different way, or in the wake of the extinction of another lineage. - occur because a lineage is temporarily free from the usual constraints of interspecific competition-and the products of speciation events can exploit underutilized, or completely novel, ecological niches in the environment. - An adaptive radiation of mammals followed the extinction of the dinosaurs. - An adaptive radiation of dinosaurs followed the extinction of the land crocodiles and mammal-like reptiles that preceded them. - An adaptive radiation of pterosaurs occurred in response to the evolution of flight. EXAMPLE: honeycreepers

tropical rainforest

- cover 6% of the Earth's land area, and harbor a significant proportion of its biodiversity, and account for a great deal of its primary productivity. - more than 4/5 of all plant species and animals and nearly half of all animal species reside here. mystery due to: - History, - Productivity - A heterogeneous environment, with biodiversity begetting more biodiversity. EXAMPLE: Surinam rainforest

The Microbial world

- the definition of a species needs to be reconsidered when dealing with microbial fauna, because prokaryotes (which make up the lion's share of these organisms) do not reproduce sexually, and have systems of gene exchange that do not lend themselves to distinct boundaries among species. - Additionally, most microbes cannot be cultured in the laboratory setting. - Challenging environments, such as glaciers, deep drilling cores, and hydrothermal vents, have yielded unexpected biodiversity. - A big issue is in defining microbial diversity. It is very sensitive to which species concept is applied.

Cladogenesis

- the origin of lineages, is the formation of a new branch on the tree of life. Speciation is the mechanism for clagogenesis. - New species go on to speciate, in turn. - promotes biological diversity by increasing the number of species. - Extinctions pare down the number of species present on the planet, and thus, a lineage, such as mammals, with thousands of species, originally started as a single species.

Megafauna Extinction 3 Hypotheses

1) climate change 2) human hunting 3) some combination of human presence and habitat change EXAMPLES: wooly rhinoceros, shasta ground sloth

4 species concepts

1- Biological "Species are groups of actually or potentially interbreeding individuals that can mate and produce fertile offspring." 2- Phylogenetic A species is the smallest set of organisms that share a common ancestor, and can be distinguished from other such sets. 3- Morphological Species are collections of living organisms that have certain morphological and biochemical traits in common. 4- Ecological A species is a set of organisms, adapted to a set of resources, called a niche, in the environment.

species are a group of organisms that:

1-can interbreed and produce fertile offspring (biological species concept) and/or 2-share a set of traits in common that distinguishes them from other such groups (morphological species concept) and 3-is an evolutionary lineage that persists, ancestor to descendant, over time (systematic concept) 4- have a distinct place in nature (ecological concept)

This is called a latitudinal gradient in species diversity

A number of hypotheses have been proposed: 1) greater productivity in tropics 2) history 3) complexity of habitats 4) less disturbance 5) area effects, or the mid-domain effect (the area in the middle of extreme environments has the most potential for range overlap of species)

allopatric vs sympatric speciation

Allopatric Speciation: Involves a geographic barrier. Sympatric Speciation: Does not involve a geographic barrier.

allopatric speciation

Allopatric speciation involves a geographic barrier that physically isolates populations of a species and blocks allele flow. Once isolated, allopatric populations (living in different places) accumulate genetic differences due to natural selection, sexual selection, genetic drift, and new mutations.

Taxanomic Hierarchy

Every species has a place in the taxonomic heirarchy: Human Mud-Dauber Species Homo sapiens Trypoxylon politum Genus Homo Trypoxylon Family Hominidae Crabronidae Order Primates Hymenoptera Class Mammalia Insecta Phylum Chordata Arthropoda Kingdom Anamalia Anamalia Domain Eukarya Eukarya

Global biodiversity

Exhibits Several Well-Documented Patterns - Latitudinal gradient - Broad, geographical realms determined by history

latitudinal gradient

For most, but not all groups of organisms, biodiversity increases from the poles to the tropics (it tends to peak, for most organisms, in the low, northern latitudes.

Broad and Narrow Niches and Limits of Adaptation

Generalist species - broad niche Specialist species - narrow niche, more extinction-prone under changing environmental conditions

Tree of Life scientifically

In scientific terms, the tree of life is a circular diagram representing the actual diversification of organisms from a common ancestor.

Examples of Physiological Factors Limiting Distribution

Palms- Members of the palm family (Arecaceae) are widespread throughout the tropics and subtropics, but are absent from temperate areas where winter temperatures regularly go below freezing. - The meristems of palms (the "hearts of palm") occur at the top of the trunk, and are not tolerant of freezing-so palms cannot take a Northern winter. - Different palm species occupy different microenvironments. Typically, palms grow best, and compete well, in moist microenvironments. - Seed dispersal also plays a role. For instance, coconut palms have a very widespread distribution, because their seeds are water-dispersed, and can float in the ocean for months. - For this reason, wild populations of coconut palms tend to occur on beaches, close to the waves.

Phylogeny, systematics, taxonomy

Phylogeny: The phylogeny of a group is a "family tree" describing how species are related. The branching pattern of different groups of organisms is caused by repeated cladogenesis. Systematics is the study of phylogeny. Taxonomy: Is the process of describing and naming organisms. Our modern process of taxonomy is based on phylogeny, so an understanding of phylogenetic relationships-names reflect relatedness.

postzygotic isolation

Postzygotic isolating mechanisms act after a mating has occurred, to prevent fertilization or to prevent potential hybrids from passing on their genes.

prezygotic isolation

Prezygotic isolation mechanisms prevent mating, so that gametes of sympatric species never form hybrid zygotes.

History of Biogeography

Shows: - Global patterns driven by history (also local) - A general trend of increase over time, with setbacks due to mass extinction. - Adaptive radiation - Evolutionary convergence

sympatric speciation

Sympatric speciation results from intrinsic factors, such as chromosomal changes and nonrandom mating. Sympatric populations become genetically isolated even though their ranges overlap.

The Holocene Mass Extinction

The current pulse of the mass extinction we are facing occurring because of our impact on the biosphere itself. - We are living in large numbers, and causing impact to nearly every ecosystem on the planet. - The current mass extinction has the potential to eliminate 50% of all species on Earth.

biodiversity pump

The latitudinal diversity gradient may be all about temperature, humidity, insects (invertebrates) and plants - a biodiversity pump - Evolutionary arms race between insects and plants - Plants create diverse habitats for herbivorous insects. - Insect specialization selects for higher plant diversity - This interplay amplifies up the food chain

The Old Classification

This "five kingdom" scheme of classification replaced the old animal kingdom vs. plant kingdom scheme in the 1970's. It is an excellent grouping of organisms based on their characteristics, but it does not reflect evolution very well. (prokaryotes, eukaryotes, plants, animals, fungi)

The New Classification

Three large groups called domains Bacteria - prokaryotes Archaea - prokaryotes Eukarya - eukaryotes Prokaryotic - cells lack a nucleus. - Most of the true diversity on the planet is among prokaryotes Eukaryotic - cells possess a nucleus and membrane bound organelles - This group is "nested within" the Archaea.

doubly autoploidy example

Wheat is doubly autopolyploid, the product of an interspecific hybridization, then a doubling of chromosomes, then another interspecific hybridization, then another doubling of chromosomes, to produce a fertile hexaploid.