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Chapter 4 – Organism and Population Ecology and Evolution Photograph by Roger Rothweiler (my brother) Antarctica 2008 Genetic Change and Population Growth—Fact and Fiction • Population growth – European rabbit in Australia • Non-native with few predators • Population exploded • Genetic change – DNA controls growth and development – Environment can alter DNA • Frogs in Great Lakes – Pesticides © 2013 Pearson Education, Inc. 4.1 The Cell—The Fundamental Unit of Life • The cell – Fundamental unit of life • Cell structure categorizes • Prokaryotes – Small, single celled, DNA in single chromosome • Eukaryotes – Single or multicelled – Membrane-enclosed organelles – DNA in multiple chromosomes © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.1 The Cell—The Fundamental Unit of Life • Chemical functions – Photosynthesis • • • • Used by plants and some protists and bacteria Uses sunlight, CO2, and H2O Produces carbohydrates (sugars) and O2 Carbohydrates power cellular processes © 2013 Pearson Education, Inc. 4.1 The Cell—The Fundamental Unit of Life • Chemical functions –Chemosynthesis • Creates sugars from inorganic chemicals, CO2 and O2 • Used by bacteria in ecosystems with no light – Ocean depths © 2013 Pearson Education, Inc. 4.1 The Cell—The Fundamental Unit of Life • Chemical functions – Cellular respiration • • • • Carbohydrates broken to power functions Releases CO2 and H2O Nearly all organisms use Requires oxygen (aerobic) – Anaerobic respiration • Works without O2 • Yields less energy © 2013 Pearson Education, Inc. 4.2 The Growth and Reproduction of Organisms • Asexual reproduction – Simple cell division – Genetically identical offspring • Sexual reproduction – Requires two individuals • Gametes produced to form a zygote – Genetically diverse offspring © 2013 Pearson Education, Inc. 4.3 The Growth of Populations • Population Growth – Growth Rate = (Births + Immigration) – (Death + Emigration) – Birth rate–births – Death rate (mortality rate) – Immigration rate • Number entering population – Emigration rate • Number leaving population © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.3 The Growth of Populations • Patterns of growth – Exponential growth • Growth accelerates with each generation – Arithmetic growth • Growth is constant – Population growth rate • Percentage of change – Doubling time © 2013 Pearson Education, Inc. 4.3 The Growth of Populations • Exponential Growth: A Case Study • 1890, 60 European starlings released in NYC • 10 years later, tens of thousands • 1920s millions of starlings across New England • 1970 starlings across entire United States • Exponential growth © 2013 Pearson Education, Inc. 4.3 The Growth of Populations • Survivorship – Probability of an organism dying during a particular interval – Species survivorships vary widely • • • • Starling vs. bald eagle Type I–most die old Type II–young and old die equally Type III–most die young © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.3 The Growth of Populations • Fertility rate – Rate of reproduction • Changes with age • Age-specific fertility rates – Offspring produced at age ranges • Total fertility rates – Potential number offspring – Generation time • Time between mothers and offspring © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.4 Limits on Population Growth • Populations cannot grow forever – Limits to growth • Carrying capacity – The number of organisms the environment can support • Results in logistic growth curve (S shape) • Competition reduces reproduction rate © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.4 Limits on Population Growth • Not all populations exhibit an S curve – Some exceed carrying capacity • Populations fluctuate around carrying capacity – Some shoot past carrying capacity • Population then crashes – Rather common © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.4 Limits on Population Growth • Other limits on population growth – Temperature – Space – Chemicals/nutrients • Range of tolerance – Span between minimum and maximum values for survival © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.4 Limits on Population Growth • Range of tolerance for various factors determine habitat and niche. • Habitat – Environment organism depends on • Temperature, humidity, living elements • Niche – Role organism fills © 2013 Pearson Education, Inc. 4.5 Evolution and Natural Selection • Species evolve – Adaptations • Inherited structure, functions, behaviors – Give survival, reproductive advantage – Natural selection • Most fit leave more offspring, their adaptation becomes more common • Less fit have fewer offspring, their adaptation becomes less common © 2013 Pearson Education, Inc. 4.5 Evolution and Natural Selection • Biological evolution may occur rapidly – Recent studies on Darwin's finches • Droughts caused rapid evolution • Return of rains reverted population © 2013 Pearson Education, Inc. 4.5 Evolution and Natural Selection • Source of natural variations – Mutations • Chance changes in DNA, • Environmental influence – UV radiation, chemicals, pollution • Random © 2013 Pearson Education, Inc. 4.5 Evolution and Natural Selection • Three types of natural selection – Directional selection • One extreme end of range of variation favored – Stabilizing selection • Middle range of variation favored – Disruptive selection • Both extremes ends of the variation are favored over the average traits © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.5 Evolution and Natural Selection • Other sources of genetic change –Random events alter frequency of variations –Small population susceptible –Genetic drift • Founder effect –Genetics change from immigration of small group © 2013 Pearson Education, Inc. 4.6 The Evolution of Species • Species–organisms that can breed and produce fertile offspring • New species – Reproductive isolation • Breeding barriers – Geographic • Mountains, rivers – Temporal • Breeding seasons © 2013 Pearson Education, Inc. 4.6 The Evolution of Species • New species – Reproductive isolations • Behavioral – Courtship rituals • Structural – Genital compatibility © 2013 Pearson Education, Inc. 4.7 The Hierarchy of Life • Taxonomy – Classification of organisms • Description, identification, and naming • Hierarchical system – Shows evolutionary relationship – Each level includes level below – Each species given two-part name – Genus species, • Example: Lepus townsendii, Homo sapiens © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4.7 The Hierarchy of Life • Organisms classified based on evolutionary ancestry – Phylogenetic trees depict ancestry • Show physical characteristics that classify • Physical characteristics must reflect evolutionary ancestry © 2013 Pearson Education, Inc.