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Chapter 5 Evolution of Biodiversity Which was the earliest form of life? a. b. c. d. e. The eukaryotic cell The protocell The prokaryotic cell The amino acid The RNA Biodiversity Biodiversity increases with speciation decreases with extinction Give-and-take between speciation and extinction changes in biodiversity Extinction creates evolutionary opportunities for adaptive radiation of surviving species Earth is home to a tremendous diversity of species • • • Ecosystem diversity- the variety of ecosystems within a given region. Species diversity- the variety of species in a given ecosystem. Genetic diversity- the variety of genes within a given species. Types of Diversity Which does not belong? • • • • A. Situational B. Ecosystem C. Genetic D. species • • Species richness- the number of species in a given area. Species evenness- the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals. Evolution is the mechanism underlying biodiversity • • • Evolution- a change in the genetic composition of a population over time. Microevolution- evolution below the species level. Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla. Evolution is the mechanism underlying biodiversity • MacroevolutionEvolution which gives rise to new species or new genera, family, class or phyla. Speciation • Happens when there is reproductive isolation between 2 populations • May be because of geographics, behavioral, or temporal issues Evolution by artificial selection • Evolution by artificial selection- when humans determine which individuals breed.. Evolution by natural selection • Evolution by natural selectionthe environment determines which individuals are most likely to survive and reproduce. Darwin’s theory of evolution by natural selection • • • • • Individuals produce an excess of offspring. Not all offspring can survive. Individuals differ in their traits. Differences in traits can be passed on from parents to offspring. Differences in traits are associated with differences in the ability to survive and reproduce. Which of the following statements does not belong to the theory of Natural Selection? • A. • B. More species are made than survive N.S. happens when a particular breed of dog is created by Man. • C. The best adapted organism survives in order to reproduce more of its kind. • D. According to N.S. theory, the less fit do not survive, therefore, do not evolve. Specialized Feeding Niches • Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-8 Evolution shapes ecological niches and determines species distributions • • • Range of tolerance- all species have an optimal environment in which it performs well. The limit to the abiotic conditions they can tolerate is known as the range of tolerance. Fundamental niche- the ideal conditions for a species. Full potential of physical, chemical, and biological conditions an organism could use. Realized niche- the real part of the niche that an organism occupies to avoid and survive competition. Niches • • • Realized niche- the range of abiotic and biotic conditions under which a species lives. This determines the species distribution, or areas of the world where it lives. Niche generalist- species that live under a wide range of conditions. Niche specialist- species that live only in specific habitats. • Generalist species tolerate a wide range of conditions. • Specialist species can only tolerate a narrow range of conditions. Figure 4-7 Adaptive Radiation •Emergence of numerous species from a common ancestor introduced to new and diverse environments. •Example: •Hawaiian Honeycreepers The Fossil Record • Fossils- remains of organisms that have been preserved in rock. Much of what we know about evolution comes from the fossil record. SPOTLIGHT Cockroaches: Nature’s Ultimate Survivors • 350 million years old • 3,500 different species • Ultimate generalist • Can eat almost anything. • Can live and breed almost anywhere. • Can withstand Figure 4-A Which type of species is the cockroach? • A. Generalist species • B. Specialist species • C. Naturalist species Cenozoic Era Period Millions of years ago Quaternary Today Tertiary 65 Mesozoic Cretaceous Jurassic 180 Triassic Species and families experiencing mass extinction Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct Extinction within the next 50–100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. Bar width represents relative number of living species 250 Extinction 345 Extinction Permian Paleozoic Carboniferous Devonian Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. Silurian Ordovician Cambrian 500 Extinction Ordovician: 50% of animal families, including many trilobites. Fig. 4-12, p. 93 At any given moment (e.g. the ‘present’), all we see is current diversity… all extinct forms are gone (99.9%) The Sixth Mass Extinction • • • Scientists feel that we are in our sixth mass extinction, occurring in the last two decades. Estimates of extinction rates vary widely, from 2 % to 25% by 2020. In contrast to previous mass extinctions, scientists agree that this one is caused by humans.