Chapter 4 Ecosystems and Living Organisms

1. Chapter 4Ecosystems and Living Organisms

2. Overview of Chapter 4 • Evolution • Natural Selection • Domains and Kingdoms • Biological Communities • Primary & Secondary Succession • Symbiosis • Mutualism, Commensalism, Parasitism • Predation & Competition • Resource Partitioning • Keystone Species • Species Richness & Community Stability

3. Evolution • The cumulative genetic changes that occur in a population of organisms over time • Current theories were proposed by Charles Darwin, a 19th century naturalist • Evolution occurs through natural selection • Natural Selection • Individuals with more favorable genetic traits are more likely to survive and reproduce • Frequency of favorable traits increase in subsequent generations

4. Natural Selection • Based on four observations about the natural world • Overproduction • Each species produces more offspring than will survive to maturity • Variation • Individuals in a population exhibit variation • Limits on Population Growth • Resource limitations will keep population in check • Differential Reproductive Success • Individuals with most favorable traits are more likely to reproduce

5. Natural Selection • Darwin’s finches exemplified the variation associated with natural selection

6. Domains and Kingdoms of Life

7. Biological Communities • Communities vary greatly in size and lack precise boundaries • They are often nestled within each other

8. Succession • The process where a community develops slowly through a series of species • Earlier species alter the environment in some way to make it more habitable by other species • As more species arrive, the earlier species are outcompeted and replaced • Two types of succession • Primary succession • Secondary succession

9. Primary Succession • Succession that begins in a previously uninhabited environment • No soil is present! • Ex: bare rocks, cooled lava fields, etc. • General Succession Pattern • Lichen secrete acids that crumble the rock (soil begins to form) Lichen mosses grasses shrubs forests

10. 1 2 • Primary Succession • Bare rock with lichen • Grasses and shrubs • Forest community 3

11. Secondary Succession • Succession that begins in an environment following destruction of all or part of the earlier community • Ex: abandoned farmland, open area after fire • Does NOT follow primary succession! • Even though name may imply this • Generally occurs more rapidly than primary succession

12. Secondary Succession of an abandoned farm field in North Carolina

13. Interactions Among Organisms • Symbiosis • An intimate relationship between members of 2 or more species • Participants may be benefited, harmed or unaffected by the relationship • Results of coevolution is the interdependent evolution of two interacting species. Flowering plants and their animal pollinators have a symbiotic relationship that is an excellent example of coevolution. • Three types of symbiosis • Mutualism • Commensalism • Parasitism

14. Mutualism • Symbiotic relationship in which both members benefit • Ex: Mycorrihzal fungi and plant roots • Fungus grows around and into roots providing roots with otherwise unavailable nitrogen from soil • Roots provide fungi with food produced by photosynthesis in the plant Left: root growth without fungi Right: root growth with fungi

15. Commensalism • Symbiotic relationship where one species benefits and the other is neither harmed nor helped • Ex: epiphytes and tropical trees • Epiphytes anchors itself to the tree, but does not take nutrients from the tree • Epiphyte benefits from getting closer to sunlight, tropical tree is not affected

16. Parasitism • Symbiotic relationship in which one species is benefited and the other is harmed • Parasites rarely kill their hosts • Ex: Varroa mites and honeybees • Mites live in the breathing tubes of the bees, sucking their blood and weakening them

17. Predation • The consumption of one species by another • Many predator-prey interactions • Most common is pursuit and ambush • Plants and animals have established specific defenses against predation through evolution

18. Pursuit and Ambush • Pursuing prey simply means chasing it down and catching it • Ex: Day gecko and spider (see picture) • Ambush is when predators catch prey unaware • Camouflage • Attract prey with colors or light

19. Plant Defenses Against Predation • Plants cannot flee predators • Adaptations • Spikes, thorns, leathery leaves, thick wax • Protective chemicals that are poisonous or unpalatable

20. Animal Defenses Against Predation • Fleeing or running • Mechanical defenses • Ex: quills of porcupines, shell of turtles • Living in groups • Camouflage • Chemical defenses- poisons • Ex: brightly colored poison arrow frog

21. Competition • Interaction among organisms that vie for the same resource in an ecosystem • Intraspecific • Competition between individuals in a population • Interspecific • Competition between individuals in 2 different species

22. Ecological Niche • The totality of an organisms adaptations, its use of resources, and the lifestyle to which it is fitted • Takes into account all aspect of an organisms existence • Physical, chemical, biological factors needed to survive • Habitat • Abiotic components of the environment • Ex: Light, temperature, moisture

23. Ecological Niche • Fundamental niche • Potential idealized ecological niche • Realized niche • The actual niche the organism occupies • Ex: Green Anole and Brown Anole

24. Ecological Niche • Green Anole and Brown Anole • Fundamental niches of 2 lizards initially overlapped • Brown anole eventually out-competed the green anole- reduced the green anole’s realized niche

25. Limiting Resources • Any environmental resource that, because it is scarce or at unfavorable levels, restricts the ecological niche of an organism

26. Interspecific Competition

27. Competitive Exclusion & Resource Petitioning • Competitive Exclusion • One species excludes another from a portion of the same niche as a result of competition for resources • Resource Partitioning • Coexisting species’ niche differ from each other in some way

28. Keystone Species • A species that exerts profound influence on a community • More important to the community than what would be expected based on abundance • The dependence of other species on the keystone species is apparent when the keystone species is removed • Protecting keystone species is a goal to conservation biologists

29. Species Richness • The number of species in a community • Tropical rainforests = high species richness • Isolated island = low species richness • Related to the abundance of potential ecological niches

30. Ecosystem Services • Important environmental benefits that ecosystems provide, such as: • Clean air to breathe • Clean water to drink • Fertile soil in which to grow crops