Intro to ENV chapter 3 Biodiversity and Organisms PDF

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chapter 3 presentation notes, vocab is in bold, covers Ecology and its founders, mutation, evolution, and talks about sex ratio as well as population...

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Chapter 3 ENV

Central Case Study - Hawaii’s geographic isolation in the middle of the Pacific has created a cradle of evolution. - Half of the native bird species have gone extinct since the 18th century, primarily due to human influences. - The aki is one of 18 living species of Hawaiian honeycreepers that diverged from a single ancestral species that reached Hawai’i millions of years ago. a. Each species has its own set of unique characteristics, such as bill shape. - The aki has a distinctly curved bill that it uses to get nectar from a similarly shaped flower. - Hawaiian forests are under siege due to clear-cutting and non-native species introduced first by Polynesian and then European settlers. Evolution: The Source of Earth”s Biodiversity - A species is a classification of organism whose members can interbreed and produce fertile offspring - A population is a group of individuals within a species that live in the same geographic area. - Populations change over multiple generations as genetic changes alter their physical and behavioral characteristics, a process called evolution - Evolution originates in genes and often leads to modifications in appearance or behavior Natural Selection Shapes Organisms - Evolution is driven by natural selection, a process that favors certain inherited characteristics over others, causing them to be passed on more frequently. - The idea of natural selection is based on three observations: - Organisms face a constant struggle to survive and Reproduce. - Organisms tend to produce more offspring than can survive to maturity. Individuals of a species vary in their attributes - Attributes are passed from parent to offspring through genes. - Genes that lead to better reproductive success will eventually evolve through the entire population. This is called adaptation - The concept of natural selection was first proposed in 1850 by Charles Darwin and Alfred Russel Wallace. Understanding Evolution is Vital for Modern Society - A working knowledge of evolutionary processes has - enabled us to: - Selectively breed crops and livestock. - Avoid antibiotic resistance in livestock. - Avoid pesticide resistance in crop-eating insects. - Determine how infectious diseases spread and gain or lose potency.

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Chapter 3 ENV

Selection Acts on Genetic Variation - Accidental changes in DNA, called mutations, give rise to genetic variation in individuals. - The mixing of genetic material through sexual reproduction also generates variation. a. Natural selection can drive a feature in a particular direction - Closely related species that live in different environments tend to diverge in their traits. a. Different selective pressure leads to different adaptations as certain individuals in a population will survive and reproduce at greater rates. - Unrelated species living in similar environments may independently acquire similar traits, in a process called convergent evolution a. Similar selective pressures favor similar traits Evidence of Selection is All Around Us - Humans have conducted selection under our own direction, called artificial selection a. Domesticated dogs, cats, and livestock Evolution Generates Biodiversity - Biodiversity Or biological diversity refers to the variety of life across all levels. a. Species, genes, populations, and communities. - About 1.8 million species have been identified, but the actual amount may be 3–100 million. - The process by which new species are generated is Termed speciation Speciation Produces New Types of Organisms - Allopatric speciation occurs when populations become physically separated over a geographic distance. - When a mutation arises in an organism of one of the populations, it does not spread to the other. - Eventually the populations grow so different that they can no longer mate. We Can Infer the History of Life’s Diversification - Scientists represent the history of divergence with phylogenetic trees - Constructed by analyzing genes and external traits of organisms. - Taxonomists group species into categories meant to reflect evolutionary relationships. - Related species are grouped into a genus, related genera are grouped into families, etc. Fossils Reveal Life’s History - A Fossil is an imprint in stone of a dead organism. - By dating the rock layers that contain fossils, paleontologists can learn when the organisms lived. The body of fossils worldwide is called the fossil record - The vast majority of species that once lived have disappeared due to extinction

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Chapter 3 ENV Some Species Are Especially Vulnerable to Extinction - Extinction occurs when the environment changes more rapidly than the species can adapt. - Small and narrowly specialized - populations are the most vulnerable. - For example, Hawaii’s native birds and plants did not evolve defenses against mammal predators. Species that are endemic to a particular region occur nowhere else on Earth. Earth Has Seen Episodes of MAss Extinction - Most extinction happens gradually, at a rate called the background extinction rate - The Earth has seen at least five mass extinction events that wiped out 50–95% of Earth’s species each time. - The most catastrophic was the Permian extinction, 250 million years ago. - Causes can include volcanism, asteroid impact, methane releases, and global warming The Sixth Mass Extinction is Upon Us - Many biologists have concluded that the Earth is currently entering its sixth mass extinction event. - Causes stem from human population growth: - Altering or destroying natural habitats. - Overhunting and overharvesting. - Pollution of air, water, and soil. - Introduction of non-native species. - Climate change. Ecology and the Organism - Ecology is the study of the interactions among organisms and with their environments, and includes many levels. - An organism is a single living thing. - A population is a group of individuals of the same species that live in the same area. - A Community includes all of the populations of species that live and interact within an area. - Community ecology studies these interactions. - Ecosystems include communities and all of the abiotic, or nonliving, parts of the environment. a. Ecosystem Ecology studies the flow of energy and nutrients between the living and nonliving parts. - The biosphere is the sum total of all living things and habitats on the Earth. - Landscape ecology examines how ecosystems, communities, and populations are distributed across the Earth

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Chapter 3 ENV Each Organism Has Habitat Needs - Each organism has a relationship with its habitat, the environment in which it lives. - Rock, soil, leaf litter, plant life, etc. - Depending on the species, a habitat may be a square meter of soil or many miles of land. - Organisms thrive in certain habitats and not others, creating patterns of habitat use - Mobile organisms are able to choose where they live, a process called habitat selection Organisms Have Roles in Communities - An organism’s role in its community is its niche - Includes resource use and interaction with other organisms. - Species with narrow niches are specialists - ‘akiapōlā’au specializes in digging grubs out of trees. - Species that can utilize a wider variety of resources are generalists - The common myna has an unremarkable bill that can eat many foods Population Ecology - Population size, the number of organisms in an area at a given time will grow when resources are abundant and natural enemies are few. - Declines are caused by resource loss, natural disaster, or impacts from other species. - The North American passenger pigeon declined and went extinct due to overhunting - Population density describes the number of individuals per unit area. - Population distribution describes the spatial arrangement of organisms within an area. - Random shows no particular pattern. Uniform has individuals spaced evenly. - Clumped occurs when individuals concentrate in certain areas - Sex ratio is the proportion of males to females. a. 1:1 ratios are seen in monogamous species; ratios vary in others. - age structure describes the number of individuals of different ages within a population. - This can help to predict whether a population will grow or shrink in the near future.

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Chapter 3 ENV Populations May Grow, Shrink, or Remain Stable - Population change is determined by four factors: - Natality – Births within the population. Mortality – Deaths within the population. - Immigration – Arrival of individuals from outside the population. Emigration – Departure of individuals from the Population. - A population’s rate of natural increase is determined by subtracting the death rate from the birth rate - The actual population growth rate includes the effects of emigration and immigration: (birth rate - death rate) + (immigration rate - emigration rate) - Rate may be expressed per 1000 individuals per year. These can be used in the formula - Growth rates may be expressed as percentages: Population growth rate * 100 Unregulated Population Increase by Exponential Growth - When a population increases by a fixed percentage each year, it undergoes exponential growth - When graphed, these populations produce a J-shaped curve. - Exponential growth only occurs in nature when a population is small, competition is minimal, and environmental conditions are ideal. Limiting Factors Restrain Growth

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Eventually, every population is constrained by physical, chemical, and biological limiting factors in the environment. - These factors determine carrying capacity, the maximum population size of a species that an environment can sustain. Population growth slows as it reaches the carrying capacity. This produces an Sshaped curve called logistic growth The Eurasian collared dove is a non-native species that has reached carrying capacity in Florida, where it was introduced. - In other areas, its population grows slowly or exponentially, depending on how recently it arrived. The density of a population can enhance or diminish the effect of some limiting factors. Density-dependent factors rise and fall with population density. - Predation, disease Density-independent factors are unaffected by population density. - Temperature extremes, catastrophic natural disasters

Carrying Capacities Can Change - Carrying capacities can vary, as environments and species are complex and everchanging. - If a fire destroys a forest, its carrying capacities for most animals will decrease. - By learning to build shelters and control fire, humans eased the limiting factors of cold environments and increased the planet’s carrying capacity for them

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Chapter 3 ENV

Conserving Biodiversity - Human development and resource extraction are speeding the natural rate of environmental change that affects populations. - One example is introduced species, which displace or kill native species Innovative Solution are Working Innovation Solutions Are Working - A wide variety of organizations work to protect land, remove alien species, and -

restore native habitats. These efforts can create economic benefits, as visitors are drawn to wildlife and natural areas. - This is called ecotourism. - Hawaii’s economy takes in $12 billion annually from more than 7 million visitors per year.

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Chapter 3 ENV

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