Ecosystems and living organisms

1. Ecosystems and living organisms Chapter 5

2. Evolution: populations change • Evolution: genetic change over time • Charles Darwin: traits favorable to survival would be preserved; frequency of favorable traits increase in subsequent generations • Adaptation: evolutionary modification that improves survival and reproductive success • Natural selection based on observations: overproduction, variation, limits on population growth, differential reproductive success

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

4. Bottleneck – reduced genetic variation due to reduced population size. Ex: hunting of Elephant seals. • Founder effect – when only a few organisms colonize an area. Reduced genetic variation; non-random of original gene pool

5. Check for understanding • 4 - I can explain evolution and natural selection to my peers • 3 - I understand how variation leads to varying levels of survival and over time this leads to evolution. • 2 - I understand that evolution is genetic change over time, but I don’t really get how it happens. • 1 - I am lost about natural selection and evolution

6. Succession: how communities change over time • Species in one stage being replaced over time by others; a constant process; no real climax community • Primary succession – occurs where no organisms have been before; no soil • Ex: created by volcanic lava, rock revealed by retreating glacier • Pioneer community: initial growth, typically lichens which secrete acid that breaks rock to start forming soil. • Then mosses and ferns grasses and herbs low shrubs trees. • Secondary succession – change in species composition after a disturbance has destroyed the existing vegetation; soil is already there. • Ex: after a fire, abandoned farmland

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

8. Check for understanding • 4 - I can explain succession (both primary and secondary) to my peers • 3 - I understand the difference between primary and secondary succession. • 2 - I understand primary and secondary succession but can’t give examples • 1 - I am lost about succession

9. INTERACTIONS BETWEEN ORGANISMS

10. Keystone species • A species that is more important than expected based on amount to the stability of the ecosystem than others. • Ex 1: gray wolf – their decline increased herbivore numbers when then overgrazed. Insects declined because their food (plants) were declining. • Ex 2: fig trees in tropical rain forest – animals eat figs when other fruits are not abundant • Ex 3: starfish (Pisaster ochracceus) – predator, two mussle species grow unchecked without them • Conservation efforts focus on protecting keystone species – easier to protect just one to balance an entire community.

11. 1. Symbiosis: intimate relationship between at least 2 species • A result of coevolution • Ex: plants and pollinators. Plants have nectar, pollen, color, scent. Pollinators have hairy bodies, shape of beak • Types: mutualism, commensalism, parasitism

12. Mutualism – benefits are shared • Ex: nitrogen –fixing bacteria (Rhizobium) and legumes (peas/beans); plants get nitrogen and bacteria get food source. • Ex: zooxanthellae (microscopic algae) live inside coral cells and perform photosynthesis. • Coral gets nutrients (nitrogen, carbon, oxygen) & calcium carbonate skeletons form around bodies faster with algae. • Algae get shelter and nutrients (ammonia waste from coral and carbon dioxide)

13. Mutualism • Ex: Mycorrhizaefungi and plant roots • Fungus provides better absorption of water and minerals (like phosphorus) • Roots provide fungi with food (sugar) produced by photosynthesis in the plant Left: root growth without fungi Right: root growth with fungi

14. Commensalism – taking without harming • Ex: epiphytes on trees. Epiphytes gain location for light, water, nutrients but doesn’t affect tree

15. Parasitism – taking at another’s expense • Rarely kills host • A factor in the decline of honeybees (in addition to pesticides and habitat fragmentation) • Disease/death causing = pathogen Parasitic mites in bee’s trachea

16. Other interactions 2. Predation • Result’s in “arms race”; genetic changes to help capture prey or avoid predator • Adaptations: • Pursuit – better hunting efficiency (like speed)  larger brains than prey • Ambush – camouflage or attracting prey (anglerfish) • Plant defenses – thorns, waxy leaves, toxins (nicotine, opium poppy) • Animal defenses – shell, speed, herds, chemicals, camouflage

17. 3. competition: more than one individual try to use the same resource • Intraspecific competition: within population • Interspecific competition: between species

18. Check for understanding • 4 - I can explain at least 4 different ways organisms interact to my peers • 3 - I understand many different ways organisms interact and can give examples of each. • 2 - I understand different interactions between organisms but can’t give examples • 1 - I am lost about how organisms interact.

19. Ecological niche • The role an organism plays in ecosystem • Includes habitat, what it eats, what eats it, what organisms it competes with, other community interactions, how it is affected by abiotic factors (light, water, temperature)

20. niche • Fundamental niche – potential/idealized • Realized niche – actual niche(less due to competition)

21. Factors determining niche • Limiting factor: any resource –scarce/unfavorable – restricts ecological niche.

22. Competitive exclusion – due to competition, one species is excluded from a portion of the niche. (interspecific competition) • Ex: brown/green anole • Ex: paramecium – P. aureliaand P. caudatum(larger) • Resource partitioning – avoid/reduce resource competition; favored by natural selection; no two species have exact same niche

23. Interspecific Competition

24. Check for understanding • 4 - I can explain to the class the relationship between interspecific competition, competitive exclusion, and resource partitioning. • 3 - I understand interspecific competition, competitive exclusion, and resource partitioning. • 2 - I understand the definitions, but need some more practice. • 1 - I am lost about interspecific competition, competitive exclusion, and resource partitioning

25. Species richness • # of species in community; increases community stability; affected by: • Abundance of niches • Ecotone: zone between communities, increased species richness due to increased quantity of niches (edge effect) • Geographical isolation – decreases richness (smaller area decreases available niches); ex: islands, mountaintops; the more isolated and smaller in size decreases richness. • Dominance of one species reduces richness: takes resources/outcompetes other species • Environmental stress of habitat reduces richness (polluted stream)

27. Ecosystem services • what ecosystems do for other organisms, including humans • Greater species richness = better ecosystem services • Ex: provide habitat, forests provide wood, purify air/water and absorb CO2, grasslands provide humans with livestock, rivers provide recreation and methods of transportation

29. Check for understanding • 4 - I can explain to the class how ecosystem services are related to species richness. • 3 - I understand factors that influence species richness and can define ecosystem services. • 2 - I either understand only species richness or ecosystem services, but not both fully. • 1 - I am lost about ecosystem services and species richness