Maintaining a Balance Topic 2 : Environmental Changes

1. Maintaining a BalanceTopic 2: Environmental Changes Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis

2. DOT POINT outline the impact on the evolution of plants and animals of: • changes in physical conditions in the environment • changes in chemical conditions in the environment • competition for resources

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

4. Environmental Change and Competition Evidence 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

5. Environmental Change and Competition As 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

6. Environmental Change and Competition Change in the environment of a population influences evolution because it results in selective pressure acting on organisms. Selective pressures include: • Environmental change • Competition • Predation • disease seeseeeye.csu.edu.au

7. Environmental Change and Competition Those 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

8. Environmental Change and Competition It 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. Handout world.edu

9. Physical Changes in the Environment Physical changes in the environment mat have been instrumental in the evolution of organic molecules from inorganic substances on early Earth. Urey and Miller’s experiments supported Haldane and Oparin’s 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

10. Physical Changes in the Environment The 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

11. Physical Changes in the Environment Some 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 vegetation • The 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 Australia • Dust clouds that formed as a result of a meteorite striking the Earth. world.edu

12. Physical Changes in the Environment Other 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

13. Physical Changes in the Environment Biological 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

14. Chemical Changes in the Environment The 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

15. Chemical Changes in the Environment The 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

16. Chemical Changes in the Environment The 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

17. Evolution It 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

18. Evolution Macro-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. • Canisrufus: red wolf • Canisaureus: jackal • Canisfamiliaris: dog tumblr.com

19. Evolution Micro-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

20. Evolution The 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

21. Activity Handout 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 homeworkusing the scaffold provided.