Planet Earth and Its Environment A 5000-million year Journey

Biology in Focus, HSC CourseGlenda Childrawi, Margaret Robson and Stephanie Hollis

Maintaining a BalanceTopic 2: Environmental Changes1DOT POINToutline the impact on the evolution of plants and animals of:changes in physical conditions in the environmentchanges in chemical conditions in the environmentcompetition for resources

IntroductionSince evolution involves change over time, a key question that arises is:What factors are thought to bring about evolutionary change?blog.makezine.com

Environmental Change and CompetitionEvidence suggests that change in the environment is a driving force behind change in living organisms. The environment can be described as the living (biotic) and non-living (abiotic) surroundings of an organism. pacificvoyagers.org

Environmental Change and CompetitionAs a result of environmental change, resources may become limited and so living organisms will begin to compete for the available resources in order to survive. Competition will arise between organisms for resources such as light, soil nutrients and water in plants, or food, water, shelter, mates and breeding territory in animals. costaricaoutwardbound.org

Environmental Change and CompetitionChange in the environment of a population influences evolution because it results in selective pressure acting on organisms. Selective pressures include:Environmental changeCompetitionPredationdiseaseseeseeeye.csu.edu.au

Environmental Change and CompetitionThose organisms that compete most successfully for available resources survive to breed and therefore to pass on their genes to the next generation. That is, those individuals that compete successfully in the new environment outlive those that do not have such variations. Such organisms are said to have an adaptation to the changed environment.naturallycuriouswithmaryholland.wordpress.com

Environmental Change and CompetitionIt is important to remember that an individual does not develop an adaptation in response to the environmental change the organisms already possess the random variation that confers an advantage under the new conditions. This variation is now called an adaptation because it enables the organisms that possess it to cope better with the selective pressure of the new environment and out-compete those organisms that do not possess it. world.eduHandout

Physical Changes in the EnvironmentPhysical changes in the environment mat have been instrumental in the evolution of organic molecules from inorganic substances on early Earth. Urey and Millers experiments supported Haldane and Oparins theory that organic compounds may have formed on Earth in the presence of strong UV radiation, electrical energy from lightning and high temperatures from volcanic eruptions.spaceprime.com

Physical Changes in the EnvironmentThe reduced incidence of UV radiation on early Earth, as a result of the formation of the ozone layer, is thought to have played a key role in the movement of living organisms from water to land habitats. msnbc.msn.com

Physical Changes in the EnvironmentSome other physical changes in the environment are thought to have affected evolution:A change in the Australian climate from cool and wet to hot and dry, affecting the change in vegetationThe drying up of lakes in the Australian interior, leading to the evolution of plants and animals that could conserve water.The influence of fire, resulting in the survival of fire-resistant species in AustraliaDust clouds that formed as a result of a meteorite striking the Earth.world.eduPhysical Changes in the EnvironmentOther physical factors, such as severe changes in temperature and sea levels during the ice age, are believed to have been driving force behind the evolution of may life forms. realclimate.org

Physical Changes in the EnvironmentBiological factors may also influence evolution. For example, the arrival of humans and their hunting may have contributed to the extinction of the Megafauna. Often introduced species compete with local species and, if successful, can out-compete them and cause their elimination. en.wikipedia.org

Chemical Changes in the EnvironmentThe first life forms are believed to have lived in an anoxic (oxygen free) environment and some of these primitive life forms began to produce carbon dioxide as a result of their metabolism. tumblr.com

Chemical Changes in the EnvironmentThe appearance of carbon dioxide in the environment led to the emergence of photosynthetic organisms the precursors to plants. They used this carbon dioxide in their metabolism and produced oxygen as a by-product. anbg.gov.au

Chemical Changes in the EnvironmentThe increasing oxygen levels in the environment led to the evolution of organisms that were aerobic organisms that could use oxygen in their respiratory pathway. Since aerobic respiration generates far more energy than anaerobic respiration, these organisms could grow larger and more complex, leading to the great diversity of aerobic life forms that we know today, including all animals. 500px.com

EvolutionIt is commonly accepted that physical and chemical changes in the environment may have been responsible for the evolution of organisms from ancient forms to forms that we know today, but they may also have been responsible for the very origins of life itself. Evolution can be considered over very long periods of time and over shorter periods of time.prote.cz

EvolutionMacro-evolution takes place over millions of years, measured as geological time, and results in the arising of new species, and even in larger groups such as families and orders. An example is the evolution of the red wolf, jackal and dog from a common ancestor. Each is a separate species belonging to the genus Canis.Canis rufus: red wolfCanis aureus: jackalCanis familiaris: dogtumblr.com

EvolutionMicro-evolution takes place over shorter periods of time and results in changes within populations, but it does not produce new species. New forms that arise within populations are sometimes referred to as varieties or races. An example is the different breeds of dogs, which all belong to the same species. halleethehomemaker.com

EvolutionThe influence of physical and chemical change in the environment on micro-evolution is significant. It is evident in examples of living organisms that we study today and helps us to understand the concepts of convergent and divergent evolution, and to explain modern examples of natural selection.staff.jccc.net

ActivityHandout and discuss the Modelling Natural Selection task and 1.1 Model of Natural Selection DOT Point scaffold.

-Students are to plan and carry out this investigation themselves for homework using the scaffold provided.