week 6 evolution

7/29/2019 Week 6 Evolution

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Week 6

SYCPA Regents Prep

LivingEnvironment

Evolution & Human Impact


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Week 6 Evolution & Human Impact

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Evolution Review

Natural Selection

Vocabulary:adaptations, common ancestors, competition, classification, evolution, extinction, fossils, fossil

record, natural selection, overproduction, reproduction, selecting agent, speciation, species, survival of the fittest,variations

Evolution, the change of species over time, is the central unifying theme of biology. Biological evolution occursthrough natural selection. Natural selection is the result of overproduction of offspring having variations, thesevariations struggling for survival, and the subsequent survival and increased reproduction of those best adapted to

a particular environment.

Natural selection is the evolutionary process which selects the variation(s) of organisms best suited for aparticular environment. Natural selection and its evolutionary consequences provide a scientific explanation forthe fossil record of ancient life, as well as for the molecular and structural similarities observed among the diverse

species of living organisms.

The degree of kinship between organisms or species can be estimated from the similarity of their DNA sequences;this similarity often closely matches organisms' or species' classification based on anatomical similarities.

DNA Sequence Similarities in Some Primates

The graphic above shows that:

1. All of these primates had a common ancestor, the ancestral primate.2. The human and chimpanzee have the closest evolutionary relationship as their

DNA is the most similar.


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Theory of Natural Selection

1. Overproduction: Within a population more offspring are born than can possibly survive.2. Competition: Since the number of individuals in a population tends to remain constant from generation

to generation due to limited resources, a struggle for survival occurs.3. Survival of the Fittest: The individuals who survive are the ones best adapted to exist in their

environment due to the possession ofvariations that best suit them to their environment. This geneticvariability within a species is chiefly due to mutation and genetic recombination. The variation oforganisms within a species increases the likelihood that at least some members of the species will survive

under changed environmental conditions.4. Reproduction: Variations assist or hinder individuals in their struggle for survival. The best adapted

individuals survive and reproduce, passing on the favorable variations to their offspring.

5.

Speciation: As time and generations continue, adaptations are passed on and new species may evolvefrom a common ancestor.

Small differences between parents and offspring can accumulate in successive generations so that descendantsbecome very different from their ancestors.

An adaptation is a variation which assists an organism or species in its survival. Biological adaptationsinclude changes in structures, behaviors, or physiology that enhance survival and reproductive success in a

particular environment.

Some characteristics give individuals an advantage over others in surviving and reproducing, and the advantagedoffspring, in turn, are more likely than others to survive and reproduce. The proportion of individuals that have

advantageous characteristics will increase.

Behaviors have evolved through natural selection. The broad patterns of behavior exhibited by organisms haveevolved to ensure reproductive success.

Modern Examples of Natural Selection

Peppered moth:


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Two varieties of peppered moth existed, a light colored and a dark colored one. As industrialization and coal burning increased, the environment in England where these moths lived

became dirtier .

The dark colored variety of the moth blended into the trees and increased in numbers, while the lightcolored moth was less adapted and decreased in numbers.

Insect resistance to insecticides:

Insecticides kill insects not resistant to the insecticide, while insects resistant to the insecticide live toreproduce. The insecticide acts as a selecting agent.

Bacterial resistance to antibiotics:

Bacteria not resistant to an antibiotic are killed by it, while resistant bacteria live to reproduce. Theantibiotic is a selecting agent for these bacteria.

Galapagos Island Finches:

Darwin developed his theory of natural selection by observing the many species of finches on theGalapagos Islands off the coast of South America. He notices similarities among all of the species, bothon the mainland and the islands but noticed distinct differences among those on different islands which heattributed to the selecting agents of the varying foods the finches ate.

After years of observations, he concluded that all of the island finches had evolved from the mainlandfinch. This has later been proven with DNA analysis of the different finches.


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Evolution and Extinction

Evolution does not necessarily mean long term progress is going to go in a certain direction. Evolutionary

changes often appear to be like the growth of a bush. Some branches survive from the beginning with little or nochange, many die out altogether, and others branch out repeatedly, sometimes giving rise to more complex

organisms.

Direction of Evolution

.

Note the divergence of the various groups from a common ancestor andthe fact that some branches became extinct.

Extinction of a species occurs when the environment changes and the adaptive characteristics of a species areinsufficient to allow its survival. The fossilrecord indicates that many organisms that livedlong ago are extinct.Extinction of a species is common; most of the species that have lived on earth no longer exist.

The Fossil Record

Fossils are direct or indirect remains of organisms preserved in media such as sedimentary rock, amber, ice, ortar. Fossils have been found that indicate organisms existed well over 3 billion years ago. These organisms weresimple, single-celled organisms. About a billion years ago, increasingly complex multi-cellular organisms began

to evolve.

The higher up you go in an undisturbed rock stratum (rock layer), the younger the rock layers become and

therefore it is believed the fossils within these layers, as compared to lower rock layers, are also younger.

Relative Dating of Undisturbed Sedimentary Rock and its Fossils

Upper strata generally contain fossils of younger, morecomplex organisms, whereas, the lower strata contain fossils of simplerlife forms. This means there is a tendency toward increasing complexity

in life forms over time.


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When comparing fossils in undisturbed strata, fossils can be found in upper strata which, although different fromfossils in lower strata, resemble those fossils. This suggests links between modern forms and older forms, as well

as divergent pathways from common ancestors.

ClassificationBiological classification is based on how organisms are related. Organisms are classified into a hierarchy of

groups and subgroups based on structural similarities and evolutionary relationships.

The species is the most fundamental unit of classification. This is a group of organisms which are close enough intheir evolutionary relationship to be capable of successful reproduction and having fertile offspring.

Mutations

Vocabulary:crossing over, mutation, natural selection

One source of the variation driving the process of evolution is mutation. Mutation is the change in DNA of an

organism which may result in that organism being different than its parents. While there are many causes ofmutations, some factors are known which rapidly increase the incidence of mutation.

The differences in species produced by mutation is a driving force in the process ofnatural selection.

Mutations are any changes in genetic material. Mutations can be caused by such agents as radiation andchemicals. When they occur in sex cells, the mutations can be passed on to offspring. Mutations occurring inother cells can be passed on to other body cells only. The experiences an organism has during its lifetimecan affect its offspring only if the genes in its own sex cells are changed by the experience.

Some Types of Chromosome Mutations

Inversion: chromosome piecesare attached upside down

Duplication: involves copying anextra section of chromosome

Translocation: chromosomepieces moved

Addition and deletion:chromosome is added or removed


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Either changes in chromosomes or genes on chromosomes changes the genetic which contributes to sources ofvariation.

Some Other Sources of Genetic Variability

In addition to mutation, other sources of the variation seen in sexually reproducing offspring include crossing overand genetic recombination during fertilization (union of egg and sperm). In crossing over which occurs in the

production of sex cells or gametes in meiosis, there is an exchange of chromosome pieces between the

chromosome pairs associated with each other in this process.

Crossing Over and Genetic Variation

Mutations, crossing over, and genetic recombination ensure that no two gametes formed as the result of sexualreproduction will be exactly the same. As a consequence, the offspring formed as a result of sexual reproductionwill exhibit variations. Some of these variations will be better suited for survival than others, thus driving the

process of biological evolution.

Variations

Vocabulary:mutations, natural selection, variations

Variations are differences between groups of organisms of one species. Mutation is one source of variationbetween different groups within a species. The variation of organisms within a species increases the likelihood

that at least some members of the species will survive under changed environmental conditions.

Sources of Variation

1.

The exchanging and recombining of genes during meiosis and fertilization result in a great variety of newpossible gene combinations from that of the parents.2. Mutations are random changes in the genes or DNA of sex cells may result in new gene combinations

creating variation in the offspring formed from these.

Only mutations that occur in sex cells can be passed on to the offspring. Mutations which occur in other cells canbe passed on to other body cells only. The experiences an organism has during its lifetime can affect itsoffspring only if the genes in its own sex cells are changed by the experience.


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Variation and EvolutionEvolution is the consequence of the following factors:

1. the potential for a species to increase its numbers2. the genetic variability of offspring due to mutation and recombination of genes3. a finite supply of the resources required for life4. the ensuing selection by the environment of those offspring better able to survive and leave offspring.

Some characteristics give individuals an advantage over others in surviving and reproducing, and the advantagedoffspring, in turn, are more likely than others to survive and reproduce. The proportion of individuals that

have advantageous characteristics will increase.

An Example of Variation Driving Natural Selection

Natural selection favors longer necks for a better chance to get higher leaves.Favored characteristic is passed on to next generation.

Original group exhibits variation in

neck length.

After many generations, the group is

still variable, but shows a generalincrease in neck length.

The variation of organisms within a species increases the likelihood that at least some members of the species will

survive under changed environmental conditions.

The great diversity of organisms is the result of billions of years of selection for favorable variations that hasfilled available niches of our planet with life forms.

Human Impact Review

Interrelationships

The Earth has limited to resources to support populations of humans and other organisms. Our ever increasing

human numbers is depleting many of our planet's resources and placing severe stress on the natural processes that

renew many of our resources.

Ecosystem ProcessesNatural ecosystems are involved in a wide variety of natural processes influencing humans and other organisms.The activities of humans in the environment are changing many of these natural processes in a harmful fashion.

Some of these natural processes and a brief description of a human influence on these processes is indicated in thetable which follows.


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Human Influence on Some Ecosystem Processes

Ecosystem Process Human Influence

Generation of SoilsAgricultural practices have exposed soil to the weather resultingin great loss of topsoil.

Control of the Water Cycle

The cutting of forests and other human activities have allowed

increased uncontrolled runoff leading to increased erosion andflooding.

Removal of WastesUntreated sewage wastes and runoff from farms and feedlots have

led to increased water pollution.

Energy Flow

Some industries and nuclear plants have added thermal pollutionto the environment. The release of some gases from the burning

of fossil fuels may be slowly increasing the Earth's temperature.(Greenhouse Effect).

Nutrient Recycling

The use of packaging material which does not break down,

burning of refuse, and the placing of materials in landfills prevents

the return of some useful materials to the environment.

Some Detrimental Human ActivitiesHumans are part of the Earth's ecosystem. Human activities can either deliberately or inadvertently alter the

balance of an ecosystem. This destruction of habitat, whether accidental or intentional, is threatening the stabilityof the planet's ecosystems. If these human influences are not addressed, the stability of many ecosystems may beirreversibly affected. Some of the ways that humans damage and destroy ecosystems are indicated in the table

below.

Some Ways Humans Adversely Influence Ecosystems

Human Influence Effect on Ecosystems

Population growth Our increasing numbers are using excessive amounts of the Earth's limited resources.

OverconsumptionIndustrialized societies are using more resources per person from our planet than peoplefrom poor nations.

Advancing

TechnologiesOften we introduce technology without knowing how it will influence the environment

Direct HarvestingThis has resulted in a large loss of rainforest and the many products associated with its

biodiversity.

Pollution Land, air, water, and nuclear pollution have had many adverse influences on ecosystems.

Atmospheric

Changes

These include the addition of Greenhouse gases mostly due to the burning of fossil fuelsand depletion of our stratospheric ozone layer.Other pollutants also have negative effects on living things.

Technological Developments

Human technologies which degrade the environment result in a loss of diversity in the living and nonlivingenvironment. Biodiversity refers to the differences in living things in an ecosystem.


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Many of our technologies and resource use practices have resulted in an irreversible loss of biodiversity.

Some examples of human activities which have negatively influenced other organisms include our land usepractices and pollution. Excessive land use decreases the space and resources available to other species on the

planet. Air, soil, and water pollution changes the composition of these environmental resources, making themharmful and unusable for other species and sometimes ourselves.

Endangered SpeciesEndangered species are those species which are threatened with destruction due to habitat destruction or other

factors. Animals which were once endangered but are presently successfully reproducing and increasing theirnumbers are the bison, gray wolves and egrets. Other endangered animals which are currently responding toconservation efforts and beginning to make a comeback are the whooping crane, bald eagle, and peregrine falcon.

Even with these successes, the future of many endangered species remains in doubt.

Exotic SpeciesThe importation of some organisms have caused problems for native organisms. Organisms which are importedinto an area from another region are called exotic species. Many examples of this are found world-wide. Somecommon examples of exotic species having negative effects would include the rabbits and deer which were

imported into Australia. These exotic species won the competition with many native herbivorous marsupials and

became nuisance species. The starling was brought into the United States from Europe. The starling has outcompeted many of our native songbirds. We also have alien invasive species which have caused problems in NewYork State. These include the plants such as the Water Chestnut, Eurasian Water milfoil, and Purple Loosestrifeand animals such as the Alewife and Zebra Mussel.

The Purple Loosestrife

Purple loosestrife is a plant native to Europe. It was brought to North America in

the early 1800's by immigrants who valued its beautiful purple flowers. It is

now a serious pest of wetlands. Once purple loosestrife enters a wetland, it takesover. Common native wetland plants, such as cattails, cannot compete with

purple loosestrife. Once these native plants are choked out, the wildlife thatdepends on them for food and shelter are also eliminated.

Use of Fossil Fuels

Fossil fuels are becoming rapidly depleted. The use of these fuels are adding to our air pollution problems. The

search and demand for additional fossil fuel resources also impact ecosystems in a negative way. Industrialization

has brought an increased demand for and use of energy.

One of the ways the increased burning of fossil fuels has had a harmful influence of the environment is by causing

an increased incidence of acid precipitation.


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How does Acid Precipitation occur?

Most acid rain influencing New York State is caused by sulfur dioxide and nitrogen dioxide pollution from theburning of fossil fuels in the Western and Midwestern United States. These gases combine with water vapor inthe atmosphere and fall back to the earth over New York and the Eastern United States as acid precipitation.

Some Problems Associated With Acid Precipitation

Destruction of limestone and marble monuments due to increased chemical weathering Acidification of aquatic ecosystems destroying the life in them Damage forests and other plants in a variety of ways

Our increased burning of fossil fuels and the release of excess carbon dioxide to the atmosphere associated with

their combustion is also contributing to the Greenhouse Effect or global warming. It is believed the increase inlevel of carbon dioxide and some other gases is not allowing much infrared or heat radiation to escape the planetinto outer space. This is causing our planet to slowly warm. The graphs in the table below show the link betweenincreasing earth carbon dioxide levels and the increase in global average temperatures.


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Relationship Between Global Temperature and Carbon Dioxide Levels

Some Consequences of Global Warming

Rising sea levels and coastal flooding Changed precipitation patterns which may result in droughts in some regions and increased levels of

crop failure An increase in insect borne diseases in temperate regions such as New York State as milder winters

fail to kill the disease carrying insects. (The increase in the incidence of West Nile virus may be anexample of this.)

Ozone DepletionCFC's (chlorofluorocarbons) are very active chemicals associated with certain human manufacturing processesand products. This CFC pollution from refrigerants and plastics are destroying our thin ozone shield high up in

our atmosphere or in the stratosphere. This layer of ozone normally shields us from excessive incoming ultravioletradiation. Some consequences of this ever increasing ozone depletion appear to be an increased incidence of skincancers and cataracts in the human population.


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Nuclear Energy

While nuclear energy avoids many of the pollution drawbacks associated with the increased burning of fossil

fuels, there are many risks associated with the use of nuclear fuels for energy. Environmental dangers exist inreference to obtaining, using, and storing the wastes from these fuels. Many of the waste products of used

nuclear fuel stay in the environment for thousands of years and release radiation which is harmful to humans orother living things. Additionally, the water used to cool many nuclear reactors must be released eventually to theenvironment. The thermal pollution associated with this released heat into the water is potentially dangerous to

the aquatic life in the area where this hot water is released.

Other Factors Influencing Environmental QualityMany different factors besides industry and resource use have influences on environmental quality. Some factors

include population growth and distribution, resource use, the capacity of technology to solve environmentalproblems, as well as economic, cultural, political, and ethical views.

Some Examples of Political or Cultural Views Influencing Environmental Quality

Wealthy people in the developed world tend to have fewer children. Some countries like China have laws concerning the number of children a couple may have without

penalty.

In some countries such as many in Latin America, families tend to be larger as birth control violatesreligious and societal norms.

In some poor cultures in third world countries, having many children is seen as a means of havingeconomic security in old age.

Improvements

Through a greater awareness of ecological principles and application of these principles to our naturalenvironment, humans can help assure there will be suitable environments for succeeding generations of life on our

planet.

Individuals in our societies will always have to make decisions on proposals involving the introduction of newtechnologies. Individuals in these societies need to make decisions which will assess the risks, benefits, trade-offs, and costs of these new technologies. The economic rewards of these technologies must be properly

balanced with any adverse consequences these new technologies may have on the environment. It may beimpossible to completely assess the consequences of introducing a new technology, but critical questions inreference to its introduction must be asked.

While the overall impact of humans on the planet's ecosystems have been negative, humans have done many

things to improve the overall quality for living things in ecosystems we have damaged or destroyed. Activitieshaving possible adverse effects on the environment in New York State are subject to review by SEQR (State

Environmental Quality Review Act). Some other ways in which humans have attempted to minimize negative

impacts or improve the ecosystems we are all a part of are listed in the table which follows.

Some Positive Influences of Humans on the Ecosystem

Sustaining endangered species by using habitat protection methods such as wildlife refuges andnational parks.

Passing wildlife management laws, such as game laws and catch restrictions. Adding lime to Adirondack lakes in an effort to neutralize their

acid pollution so the original living things in these lakes can be reintroduced.


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Design new products which meet basic needs without generating pollution. Inspection of all materials before entering the country to prevent pest introduction. Increased use of biodegradable packaging materials which will recycle themselves quickly to the

environment. Use fuels which contain less pollutants, such as low sulfur coal and oil. Remove pollutants by using such devices as afterburners or catalytic converters before they enter the

air.

Review provided by regentsprep.org

Evolution Regents Questions

August 2011


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June 2011


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Jan 2011


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Environmental Issues/Human Impact Regents Questions

Aug 2011


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June 2011


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Jan 2011


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week 6 evolution

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