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
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: Mycorrhizae fungi 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. aurelia and 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