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Transcript
Biology 1210 Lecture 4 Chapter 2 Introduction to Evolution and Ecology More on these ideas later in course Two Key Concepts Evolution: Changes that occur in organisms’ traits over time Ecology: How organisms live in their environment important The great diversity of life on earth is the result of evolution And evolution is the consequence of ecology over time 2.1 Darwin’s Voyage • In 1831, twenty Charles Darwin set out for a five year voyage around the world. • He read, thought, collected specimens, observed, and asked questions. Great Britain Europe North America Pacific Ocean Atlantic Ocean Africa Galápagos Islands Equator South America Andes Australia Cape of Good Hope Cape Horn Tierra del Fuego Tasmania New Zealand • He asked himself why fossils of South America were more similar to modern South American species than to fossils from other continents. • He observed the diversity of life on the Galápagos Islands, such as blue-footed boobies and giant tortoises. • In all Darwin observed 13 (14) different finch species in Galapagos • They differed mainly in beaks and feeding habitats and resembled finches on the mainland • He believed it was “descent with modification” from a common ancestor (evolution). Fig. 2.5 2.3 The Theory of Natural Selection • Darwin observed that – organisms produce more offspring than the environment can support – organisms vary in many characteristics – these variations can be inherited • Darwin concluded that – individuals best suited for a particular environment are more likely to survive and reproduce than those less well adapted – As a result, the proportion of individuals with favorable characteristics increases – Populations gradually change in response to the environment • Darwin called “the preservation of favorable variations” natural selection • Darwin drafted a preliminary transcript in 1842 – However, he shelved it for 16 years because of its controversial nature • Alfred Russel Wallace (1823-1913) independently developed a similar theory – Correspondence between the two spurred Darwin to publish his theory – In 1859, Darwin published On the Origin of Species in which he proposed that evolution occurs through natural selection • Fossils and the fossil record strongly support the theory of evolution • The fossil record shows that organisms have appeared in a historical sequence • Many fossils link early extinct species with species living today – These fossilized hind leg bones link living whales with their land-dwelling ancestors Hominid skull • In addition to Paleontology (the fossil record), there is an overwhelming convergence of evidence consistent with the theory of evolution from such diverse fields as – – – – – – – – Biogeography Comparative anatomy Comparative embryology Comparative physiology Genetics Geology Molecular biology etc Human Cat Whale Bat for a compilation of evolutionary data see origintalk.org or Richard Dawkins 2004 The Ancestor’s Tale – Data from different field converge Human Rhesus monkey Last common ancestor lived 26 million years ago (MYA), based on fossil evidence Mouse Chicken Frog Lamprey 80 MYA 275 MYA 330 MYA 450 MYA Figure 13.3B Chimps exact match with humans 104 aa Rhesus 1 aa difference The genes of diverse organisms have accumulated mutations that alter the DNA sequence. The longer it has been since any two species shared a common ancestor, the more differences there are. Comparative anatomy and fossil record are consistent with molecular data • When humans choose organisms with specific characteristics as breeding stock, they are performing the role of the environment – This is called artificial selection – Example of artificial selection in plants: five vegetables derived from wild mustard – Example of artificial selection: dog breeding German shepherd Yorkshire terrier English springer spaniel Mini-dachshund Golden retriever Hundreds to thousands of years of breeding (artificial selection) Ancestral dog mtDNA data is consistent with the origin of domestic dogs 15,000 years ago from a single gene pools of Old World Grey wolves in East Asia Scientists can observe natural selection in action • Evolutionary adaptations have been observed in populations of birds, insects, and many other organisms – Example: camouflage adaptations of mantids that live in different environments ***The evolution of insecticide resistance is an example of natural selection in action ***IMPORTANT Insecticide application Chromosome with gene conferring resistance to insecticide Additional applications of the same insecticide will be less effective, and the frequency of resistant insects in the population will grow Survivor The evolution of antibiotic resistance in bacteria is a serious public health concern • The excessive use of antibiotics is leading to the evolution of antibiotic-resistant bacteria – Example: Mycobacterium tuberculosis Two Key Concepts Evolution: Changes that occur in organisms’ traits over time Ecology: How organisms live in their environment important The great diversity of life on earth is the result of evolution And evolution is the consequence of ecology over time 2.4 The Beaks of Darwin’s Finches • Darwin collected finch species from the Galapagos Islands in 1835 • Darwin observed a correlation between the beaks and the food source of the birds and concluded that the beaks had been shaped by evolution Fig. 2.10 A diversity of finches on a single island 2.4 The Beaks of Darwin’s Finches • In 1938, David Lack set out to test Darwin’s hypothesis • Lack’s five-month observation seemed to contradict Darwin’s proposal – Lack found many different species of finch feeding together on the same seeds • So was Darwin wrong or is there something else going on? 2.4 The Beaks of Darwin’s Finches • In 1973, Peter and Rosemary Grant embarked on a study of the medium ground finch – Geospiza fortis feeds preferentially on small tender seeds abundantly available in wet years – It resorts to larger, harder seeds in dry years • The Grants found out that the beak depth changed predictably year after year 2.4 The Beaks of Darwin’s Finches Fig. 2.11 Large-beaked finches increase in number Small-beaked finches are more common • The Grants’ research supported Darwin’s hypothesis 2.7 A Closer Look at Ecosystems • Ecosystems: the fundamental units of ecology • All organisms in an ecosystem require energy – Almost all energy comes from the sun • Energy is lost at each step of the food chain – This limits the number of steps Sun Plants Herbivores Carnivores Food chain • Raw materials are not used up when organisms die – They are recycled for use by other organisms 2.8 Species Evolve to Occupy Different Niches Within an Ecosystem •Character displacements –The changes that evolve in two species to reduce competition –This is clearly seen among Darwin’s finches bills of similar sizes when living apart bills of different sizes when living together Fig. 2.8 2.9 Patterns of Population Growth • Innate capacity for increase – The rate at which a population grows in the absence of limits – Also termed the biotic potential • Realized rate of population increase (r) – # of individuals added minus the # lost – Thus: r = (birth + immigration) – (death + emigration) Life History Strategies • The particular set of adaptations that adjusts an organism’s growth rate to its environment r-selected life history K-selected life history Rapid growth Slow growth Short lifespan Long lifespan Transient environments Stable environments Large no. of offspring Small no. of offspring No parental care Parental care Life History Strategies Fig. 2.20 K-selected life history Fig. 2.19 r-selected life history 2.10 Human Populations • Throughout most of our history, human populations have been regulated by – Food availability – Disease – Predators • Two thousand years ago, the human population was ~ 130 million – It took one thousand years for it to double – And another 650 years for it to double again 2.10 Human Populations • Starting in the 1700s, technological changes gave humans more control over their environment – These changes allowed humans to expand the carrying capacity of their habitats • Currently, the human population is growing at a rate of ~ 1.3% annually – Doubling time at this rate is only 54 years! Fig. 2.21 Population Pyramids • Human population growth is not uniform • Human lives are also shaped by resource partitioning! Consumption in the Developed World • The vast majority of the world’s population is in developing countries – However, the vast majority of resource consumption is in the developed world • This disparity can be quantified by calculating the ecological footprint – The amount of productive land required to support a person throughout his or her life Fig. 2.24 Ecological footprint of individuals in different countries Resource use by humans is now 1/3 greater than the amount that nature can sustainably replace