Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Evolution and Ecology Chapter 2 Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Outline Darwin Theory of Natural Selection  Finch Beaks Clusters of Species  Drosophila - Cichlids - Buttercups Ecology Patterns of Population Growth Life History Strategies Human Populations

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Darwin and the HMS Beagle year old Charles Darwin was selected to serve as naturalist on a five-year mapping expedition around the coast of South America.  Observed series of related but distinct forms of life on Galapagos Islands near Ecuador. - Formed an explanation that natural selection drives evolution.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Darwin’s Evidence At the time, common belief was that the earth was only a few thousand years old. Darwin was, at first, fully convinced species were immutable.  During the voyage, he became intrigued that plants and animals on the young volcanic islands resembled those on nearby South American coast.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies The Theory of Natural Selection Darwin studied Thomas Malthus who pointed out populations of plants and animals tend to increase geometrically.  Unchecked reproduction should spiral out of control. Darwin was also aware of variation and artificial selection in domesticated animals.  Proposed such selection could occur in nature (Natural Selection).

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies The Theory of Natural Selection Darwin drafted a manuscript in 1842, but shelved it until 1858 when he received a similar manuscript from Alfred Wallace.  Origin of Species published in Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Finch Beaks Darwin collected 31 finch specimens from three islands in  Ornithologist John Gould determined they were a closely related group of distinct species, all similar except for their bills. - Correspondence was found between the beaks and the food source of each specimen, leading Darwin to conclude the beaks had been shaped by evolution.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies

Clusters of Species Adaptive Radiation - Process producing a cluster of species, occupying a series of similar habitats, all evolving from a recent ancestor. Galapagos finches comprise four groups:  Ground finches  Tree finches  Warbler finch  Vegetarian finch

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Hawaiian Drosophila At least 1,250 species of Drosophila in the world; more than a quarter found only in the Hawaiian islands.  Native Hawaiian flies are closely associated with native plants. - When ancestors first reached the islands, they probably encountered many empty niches, thus facilitating diversification and speciation.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Lake Victoria Cichlid Fishes Lake Victoria was home to a cluster of over 200 cichlid species.  Researches estimate first cichlid entered the lake 200,000 years ago from the Nile. - Many species probably originated as the lake dried down 14,000 years ago, isolating populations.  Diversity reduced due to competition from exotic species.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies New Zealand Alpine Buttercups More species of Alpine Buttercups (Ranunculus) grow on two islands of New Zealand than all of North and South America combined.  Research found evolutionary mechanisms behind high diversity is recurrent isolation associated with recession of glaciers. - Repeated invasion with glaciation followed by isolation.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Ecology Earnst Haekel (1866) - Study of how organisms interact with their environment.  Populations - Individuals of the same species living together.  Communities - Populations of different species living and interacting.  Ecosystems - A collection of communities and associated non-living factors.  Biomes - Major distinct terrestrial assemblages that occur over a wide area.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Biomes

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Ecosystems Almost all energy flowing through ecosystems ultimately comes from the sun.  Sun - Plants - Herbivores - Carnivores - Food Chain  Useful energy is lost at each step, severely limiting the number of steps in a food chain.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Patterns of Population Growth Innate Capacity for Increase - Rate a population grows in the absence of limits. Realized Rate of Population Increase (r) - Number of individuals added to the population minus the number lost. r = (birth + immigration) - (death + emigration)

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Exponential Growth To determine population growth rate, r must be adjusted for population size  Population Growth rate = r N - r = realized rate of population growth - N = number of individuals in population Exponential Growth  Rapid at first, but slows down as resources become exhausted.

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Carrying Capacity Carrying Capacity (K) - Number of individuals that can be supported indefinitely in a particular area.  Population Growth Rate = r N (K-N/K) Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Life History Strategies Adaptation of reproductive rate to the env.  r - rapid growth, no stabilization  K - slow growth, reaches carrying capacity Copyright © McGraw-Hill Companies Permission required for reproduction or display Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Human Populations Throughout most of history, human populations have been regulated by food availability, disease, and predation.  Starting in 1700’s, technological changes enabled humans more control over their environment and allowed escape from the confines of logistic growth. - Expanded carrying capacity

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Population Pyramids  Demographic trends can be predicted only when a population’s age structure and sex ratio is considered. Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Uncertain Future Rapidly growing human population may constitute the greatest future challenge to our biosphere.  Key element in continued growth is un- even distribution among countries. - Rapid population growth in developing countries will increase the gap between rich and poor.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Review Darwin Theory of Natural Selection  Finch Beaks Clusters of Species  Drosophila - Cichlids - Buttercups Ecology Patterns of Population Growth Life History Strategies Human Populations

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