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ENV 1301: Week 3

by: Anna Frazier

ENV 1301: Week 3 ENV 1301

Anna Frazier
Baylor University
GPA 3.8
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About this Document

Notes from Chapter 2, 3, 4
Exploring Environmental Issues
Dr. Larry Lehr
Class Notes
environmental science, Science, Environment, Exploring Issues, 1301, week 3




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This 7 page Class Notes was uploaded by Anna Frazier on Monday January 25, 2016. The Class Notes belongs to ENV 1301 at Baylor University taught by Dr. Larry Lehr in Spring 2016. Since its upload, it has received 70 views. For similar materials see Exploring Environmental Issues in Environmental Science at Baylor University.

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Date Created: 01/25/16
Anna Frazier Tuesday, January 26, 2016 Chapter 3 Evolution: The Source of Earth’s Biodiversity - Species: a population or group of populations whose members share characteristics and can freely breed with one another to produce fertile offspring - Population: a group of individuals of a given species that live in a particular region at a particular time - Evolution: change in populations of organisms from generation to generation - Natural selection: inheriting characteristics that enhance survival and reproduction are passed on more frequently to future generations than characteristics that do not, thereby altering the genetic makeup of populations through time • Charles Darwin and Alfred Russell Wallace: first proposed the concept of natural selection in 1858 - Adaption: from one generation to another through time, characteristics, or trades, that lead to better and better reproductive success in a given environment will evolve in the population - Adaptive treat: a trait that promotes success - Mutations: accidental changes in DNA - Convergent evolution: unrelated species living in similar environments in separate locations may independently acquire similar traits as they adapt two selective pressures - Artificial selection: we have chosen animals possessing traits we like and bred them together, while calling out individuals with traits we do not like • Also known as selective breeding • Our entire agricultural system is based home artificial selection - Biodiversity: variety of life across all levels, including the diversity of species, genes, and communities - Speciation: the process by which new species are generated - Allopatric speciation: species form from populations that become physically separated over some geographic distance 1 Anna Frazier Tuesday, January 26, 2016 - Phylogenetic trees: illustrate hypotheses proposing how divergence took place - Fossil: minerals replace the organic material leaving behind an imprint in stone of the dead organisms - Fossil record: the cumulative body of fossils worldwide - Extinction: The disappearance of a species from Earth • In general, extinction occurs when environmental conditions change rapidly or drastically enough that a species cannot adapt genetically to the change; the slow process of natural selection simply does not have enough time to work. Small populations are especially vulnerable to extinction. - Endemic: species that occurred nowhere else on earth • All in all, half of Hawaii's native birds were driven extinct soon after human arrival - Mass extinction events: events of staggering proportions that killed off in massive numbers of species at once • The collision of a gigantic asteroid with the earth caused the extinction of dinosaurs, the best known mass extinction event Many biologists have concluded that earth is currently entering its sixth mass • extinction event • Because we depend on what nature has to offer, biodiversity loss ultimately threatens our own survival Ecology and the Organism - Ecology: the scientific study of the interactions among organisms and of the relationships between organisms and their environments - Biosphere: the cumulative total of living things on earth and the areas they inhabit - Ecologists: scientist to study relationships at the higher levels of this hierarchy, Mainly at the levels of the organism, population, community, ecosystem, landscape, and biosphere - Population ecology: examines the dynamics of population change in the factors that affect the distribution and abundance of members of a population - Community: an assemblage of interacting populations that inhabit the same area 2 Anna Frazier Tuesday, January 26, 2016 - Community ecology: focuses on patterns of species diversity and on interactions among species's, ranging from one-to-one interaction up to complex interrelationships involving the entire community - Ecosystems: Encompass living biotic communities and the abiotic materials and forces with which community members interact - Ecosystem ecology: addresses the flow of energy and nutrients by studying living and nonliving components of systems in conjunction - Landscape ecology: helps us understand how and why ecosystems, communities, and populations are distributed across geographic regions - Habitat: this specific environment in which an organism lives - Habitat selection: Mobile organisms actively select habitats from among the range of options they encounter - Niche: reflects a species’ use of habitat and resources, It's consumption of certain foods, Its role in the flow of energy and matter, and it's interactions with other organisms • “Habitat is the organisms address, and the niche is its profession.” - Specialist: a species with narrow breadth - Generalist: a species with broad tolerances, a “jack-of-all-trades” able to use a wide array of resources Population Ecology - Population size: expressed as the number of individual organisms present at a given time; May increase, decrease, undergo cyclical change, or remain stable over time • Populations generally grow when resources are abundant and natural enemies are few - Population density: describes the number of individuals per unit area in a population - Population distribution: The spatial arrangement of organisms in an area • Random distribution: individuals are located haphazardly in no particular pattern (resources are plentiful throughout the area) 3 Anna Frazier Tuesday, January 26, 2016 • Uniform distribution: individuals are evenly spaced (occurs when individuals compete for space) • Clumped distribution: results when organisms seek habitats or resources that are unevenly spaced - Sex ratio: a populations proportion of males to females - Age structure: describes the relative numbers of individuals of different ages within a population - Demographers: scientists who study human population - Rate of natural increase: subtract the death rate from the birthrate - Exponential growth: when a population increases by a fixed percentage each year - A population may grow exponentially when colonizing an unoccupied environment for explaining an unused resource - Limiting factors: physical, chemical, and biological attributes of the environment that restrained population growth - Carrying capacity: determined by limiting factors, this is the maximum population size of a species at a given environment can sustain - Logistic growth curve: ecologists use the Sshaped curve to show how exponential growth is slowed and eventually brought to a standstill by limiting factors - Density-Dependent: the condition of a limiting factor whose effects on a population increased or decreased depending on the population density - Density-Independent: the condition of a limiting factor is a fax on a population are constant regardless of population density Conserving Biodiversity - Ecotourism: visitation of natural areas for tourism and recreation. Most often involves tourism by more-affluent people, which may generate economic benefits for less-affluent communities near natural areas and thus provide economic incentives for conservation of natural areas 4


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