Sections 5-2 & 5-4 Evolution and Biodiversity What is Evolution?

Core Case Study Earth: The Just-Right, Adaptable Planet  Oxygen Level On earth, oxygen comprises 21 percent of the atmosphere. If oxygen were 25% fires would erupt spontaneously, if it were 15%, human beings would suffocate.  Water Vapor Levels. If water vapor levels in the atmosphere were greater than they are now, a runaway greenhouse effect would cause temperatures to rise too high for human life. If they were less, an insufficient greenhouse effect would make the earth to cold to support human life. Figure 4-1

Biological Evolution  Proposes theories about development of the variety of species we find on the earth today. Figure 4-2

How Do We Know Which Organisms Lived in the Past?  Our knowledge about past life comes from Fossils Fossils chemical analysis chemical analysis cores drilled out of buried ice, cores drilled out of buried ice, DNA analysis. DNA analysis. Figure 4-4

EVOLUTION, NATURAL SELECTION, AND ADAPTATION  Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations.  Natural selection: a difference in reproductive success of certain traits due to organisms’ interactions with their environment.  Ex.  Adaptation: an organism’s characteristics or traits that allow it to survive and reproduce in an environment.

Natural Selection and Adaptation  Three conditions are necessary for biological evolution: Genetic variability Genetic variability Traits must be heritable Traits must be heritable Trait must lead to differential reproduction. Trait must lead to differential reproduction.  An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions. Natural Selection Natural Selection

Limits on Adaptation through Natural Selection  A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce. Humans have a relatively slow generation time (decades) and output (# of young) versus some other species. Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.

Common Myths about Evolution through Natural Selection  Evolution through natural selection is about the most descendants. Organisms do not develop certain traits because they need them. Organisms do not develop certain traits because they need them. There is no such thing as genetic perfection. There is no such thing as genetic perfection.

GEOLOGIC PROCESSES, CLIMATE CHANGE, CATASTROPHES, AND EVOLUTION  The movement of solid (tectonic) plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones. The locations of continents and oceanic basins influence climate. The locations of continents and oceanic basins influence climate. The movement of continents have allowed species to move. The movement of continents have allowed species to move.

Climate Change and Natural Selection  Changes in climate throughout the earth’s history have shifted where plants and animals can live. Figure 4-6

Catastrophes and Natural Selection  Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.

SPECIATION  Speciation: Theoretically, a new species can arise when members of a population become isolated for a long period of time. Genetic makeup changes prevent them from producing fertile offspring with the original population if reunited. Genetic makeup changes prevent them from producing fertile offspring with the original population if reunited.

Geographic Isolation  …can lead to reproductive isolation, divergence of gene pools and speciation. Figure 4-10

Evolutionary Divergence  Each species has a beak specialized to take advantage of certain types of food resource. Figure 4-9

Coevolution: A Biological Arms Race  Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other. This often happens between predators and prey species. This often happens between predators and prey species. Or plants and pollinators Or plants and pollinators

Extinction: Lights Out  Extinction occurs when the population cannot adapt to changing environmental conditions.  The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate. Figure 4-11

Fig. 4-12, p. 93 Tertiary Bar width represents relative number of living species EraPeriod Species and families experiencing mass extinction Millions of years ago Ordovician: 50% of animal families, including many trilobites. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites Cambrian Ordovician Silurian Devonian Extinction Paleozoic Mesozoic Cenozoic Triassic: 35% of animal families, including many reptiles and marine mollusks. Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. Carboniferous Permian Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Extinction Triassic Jurassic Cretaceous Extinction QuaternaryToday

Definition of Biodiversity  Biodiversity is the variation of life forms life  within a given ecosystem, ecosystem biomebiome, biome or on the entire Earth. Earth  From Wikipedia:

Effects of Humans on Biodiversity  The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4-13

HUMAN IMPACTS ON TERRESTRIAL BIODIVERSITY  We have depleted and degraded some of the earth’s biodiversity and these threats are expected to increase. Figure 10-2

Fig. 10-2, p. 192 Alteration of natural chemical cycles and energy flows Indirect Effects Loss of Biodiversity Climate change Human Population Size and resource use Human Activities Agriculture, industry, economic production and consumption, recreation Changes in number and distribution of species Pollution of air, water, and soil Degradation and destruction of natural ecosystems Direct Effects

H I P P O + C  H-Habitat Loss-destruction, degradation and fragmentation  I-Invasive Species  P-Population of humans increasing  P-Pollution  O-Overharvesting  + C- Climate Change

Why Should We Care About Biodiversity?  Use Value: For the usefulness in terms of economic and ecological services.  Nonuse Value: existence, aesthetics, bequest for future generations. The Value of Biodiversity The Value of Biodiversity Figure 10-3