Population Ecology

1. Population Ecology Ch. 33.1 & 33.2

2. Target #1- I can define ecology • Ecology: the study of the interactions of organisms with each other and with their physical environment

3. Most species exist as a part of a population • Population: all the organisms of the same species interacting with the environment in a particular area • Example: all the parrotfish that live in a coral reef • Scientists might study the changes in the population over time Target #2- I can describe all the levels of ecological organization

4. Target #2- cont. • Community: all of the various populations at a particular local • Example: all of the populations of fish that live in a coral reef • Scientists might study the effects of environment on a community over time

5. Ecosystem: encompasses a community of populations, as well as the non-living environment • Biosphere: the portion of the Earth’s surface where living things exist Target #2- cont.

6. Target #3- I can state the goal of modern ecological study • The major goal of modern ecology • Develop models that explain and predict the distribution and abundance of populations and species

7. Population Ecology Ch. 33.2- patterns of population growth

8. Target #4- state how population growth is calculatedTarget #5- I can state explain biotic potential as it relates to population growth • Population sizes change over time • Represented by the growth rate • Calculated using- • (Birth rate – death rate)/ total population = population growth • Biotic potential • The highest rate of increase for a population • Factors affecting: • Average number of offspring per reproduction • Chances of survival until age of reproduction • Age at first reproduction • How often each individual reproduces

9. The Exponential Model • Involves the a pattern of increase in number due to a steady growth rate • Occurs when the birth rate exceeds the death rate • Graph characteristic • Line creates a J-shaped curve • Shows slow initial growth, and then a rapid increase in growth • Least likely to represent real populations (except for microbial growth) Target #6- I can explain the pattern described by the exponential model of population growth

10. The Logistical Model • Builds on the exponential model, but accounts for limiting factors of the environment • Carrying capacity: the number of individuals the environment can support over along period of time • Graph characteristics • S-shaped curve • When the population is small, birth rates are high and death rates are low • As the population size approaches carrying capacity, the growth rate slows • Births decrease & deaths increase • When a population reaches its carrying capacity, the birth rate equals the death rate Target #7- I can explain the pattern described by the logistical model of population growthTarget #8- I can define carrying capacity

11. Survivorship curve chart

12. Survivorship curve: a series of three curves that show the probability that members of a population will survive to a certain age • Type 1 curve the probability of dying is small until later in life • Organisms have few offspring and nurture young for extended periods of time • Example: humans or elephants Target #9- I can define survivorship curve and compare the three types of survivorship curves

13. Type 2 curve the probability of dying does not change over time • Example: birds • Type 3 curve the probability of dying when very young is high, but if organism survives through period, they will have a high chance of living to old age • Organisms have many offspring, but spend little to no time nurturing young • Example: fish and insects

14. Target #10- I can define age structure as it relates to populations • Age Structure: the distribution of individuals among different ages in a population • Often presented in graphs • The higher the number of fertile individuals, the higher the growth of the younger age brackets

15. Human Population Growth • Growth in less developed countries is still growing exponentially • There are far more young members in the population • Growth in more developed countries are at a slow growth rate or at zero population growth • Zero population growth the birthrate equals the death rate and population size remains steady • The current world population is around 7 billion people • Population ecologists predict that Earth’s carrying capacity for humans in 9 billion people, and at that point populations will begin to decrease • Evidenced when death rate exceeds birthrate Target #11- I can describe the types of population growth that occurs within the human population

17. Population Ecology Ch. 33.3- Regulation of Population Growth

18. Target #12- I can differentiate between opportunistic patterns of reproduction and equilibrium patterns of reproduction • Ecologists like to determine the factors that regulate population growth • Two types of patterns that characterize how long it takes for an organism to reach reproductive maturity and how great is the reproductive output • Opportunistic pattern • Populations are small in size, mature early, and have short life spans • Tend to produce many small offspring and to forego parental care in favor of a greater number of offspring • Example: insects, fish, weeds • Equilibrium pattern • Population size remains relatively the same, at carrying capacity • Natural selection is constantly at work because of limited resources • Organisms have a tendency to nurture their young, which are produced in smaller groups, are larger in size, slow to mature, have longer life spans • Examples: birds, mammals

19. Target #13- I can explain how limiting factors affect a population • Limiting factors like space and resources limits the growth of a population • Limiting factors are also referred to as environmental resistance • As populations grow, competition among individuals for the shrinking supply of resources intensifies • Limits the ability to reproduce

20. Target #14- I can differentiate between density-independent and density-dependent limiting factors • Two kinds of limiting factors control population size • Density-independent factors • Weather, floods, fires, et • Reduce the population by the same proportion regardless of size • Density-dependent factors • Resource limitations, like food shortages or nesting sites • Triggered by increasing population density

21. Competition • A density-dependent factor • Occurs when members of different species try to utilize a resource that is in limited supply • Ecological niche the role a species play in the community • Includes the habitat it requires and its interactions with other organisms • The resources needed to meet the energy, nutrient, survival, and reproductive demands Target #15- I can define competitionTarget #16- I can define ecological niche

22. Target #17- I can explain the competitive exclusion principle • Competitive Exclusion Principle • No two species can occupy the same ecological niche at the same time if resources are limiting • To resolve conflicts with resource sharing, feeding niches are divided by differences in habitats, reproduction periods, or migration patterns

23. Target #18- I can define predation and describe predator-prey relationships • Predation: occurs when one organism called a predator feeds on another, called the prey • Predators reduce the population density of prey • Predator and prey populations go through cycles instead of maintaining a steady state • If the predator population overkills the prey, the number of predators decreases • The prey over populates an area, and then suffers a drastic population decrease due to lack of resources

24. Target #18- cont. • Example • Snowshoe hare & Canadian lynx • The lynx feeds on the snowshoe hare • When the food source of the hare decreases, so does it’s population • When the hare population goes down, so does the lynx, which feeds on it

25. Anti-predator defenses • Coevolution • Occurs when two species adapts in response to selective pressure imposed by the other • Relates to both predator/prey relationships, and to symbiotic relationships • Examples • Cacti and holly bushes developed spines in response to predation by birds • Some organisms move in herds, or develop warning colors or signals to provide protection from predators Target #19- I can describe coevolution as it relates to anti-predator defenses

26. Mimicry • Occurs when one species resembles another species that has evolved to defend against predators or resembles an object in the environment to deceive prey • Examples • Deep sea angler fish have lures that resemble worms for the purpose of bringing fish within reach • To avoid capture, some inchworms resemble twigs or caterpillars resemble snakes • Types • Defensive • Aggressive • Reproductive • Automimicry Target #20- I can describe mimicry as it relates to anti-predator defenses

28. Population Ecology Ch. 33.3 (part 2)- Symbiosis Ch. 33.4- Ecological Succession

29. Target #21- I can differentiate between parasitism, commensalism, and mutualism • Symbiosis • Refers to the close interactions between members of two species • Types • Parasitism • Commensalism • Mutualism

30. Parasitism • A symbiotic relationship in which the parasite derives nourishment from another organism • The parasite benefits and the host is harmed • Affects on host’s health can range from slight affect up to death • Host provides shelter, a location to reproduce, and a mechanism for dispersing offspring to new hosts Target #21- cont.

31. Commensalism • A symbiotic relationship between two species in which one species is benefitted and the other is neither benefitted or harmed • Example • Clownfish live within the tentacles of sea anemones • Most fish avoid the poison the the anemone tentacles, whereas the clown fish are immune to it • The clown fish are protected from predators, but the anemone is neither harmed nor benefits from the relationship Target #21- cont.

32. Mutualism • A symbiotic relationship in which both members of the association benefit • Examples • Flowers resemble their pollinators • The flower gets pollinated and the insect or bird gets food • Cattle egrets eat insects off and around various animals, like the African cape buffalo Target #21- cont.

33. Target #22- I can define ecological succession • Ecological Succession: a change in a community’s composition that is directional and follows a continuous pattern of extinction and colonization by new species

34. Primary succession: the establishment of a plant community in a newly formed area where there is no soil formation. • Instigated by a major occurrence like a volcanic eruption or glacial retreat Target #23- I can define primary succession

35. Target #24- I can define secondary successionTarget #25- I can describe the series of steps involved with secondary succession • Secondary Succession: the return of a community to its natural vegetation following a disturbance • First species to begin the process is known as a pioneer species • Most commonly type are lichens • Succession progresses through a series of stages • 1st- grasses and mosses develop • 2nd- low lying shrubs form • 3rd- high shrubs form • 4th- shrub and tree mix • 5th- low level trees • 6th- high level trees

37. Population Ecology Ch. 34.2- Energy Flow

38. Target #26- I can identify and define the types of populations that exist within an ecosystem • Populations within an ecosystem are categorized according their food source • Autotrophs: require an outside energy source to make their food through photosynthesis • Also known as producers • Heterotrophs: need an outside food source • Also known as consumers • Types of Heterotrophs • Herbivores: animals that feed directly on plants or algae • Carnivores: animals that feed on other animals • Omnivores: animals that feed on both animals and plants • Decomposers: organisms that breakdown non-living organic matter

39. Food web • Depicts the feeding connections in an ecological community • Connects autotrophs and heterotrophs through multiple food chains • Food chain: a diagram that shows a single path of energy flow • Example Leaves caterpillars birds hawks Target #27- I can describe a food web

41. Target #28- I can describe the different types of trophic levels • Trophic level • Composed of all the organism that feed at a particular link in a food chain • 1st trophic level primary producers • 2nd trophic level-> primary consumers • herbivores • 3rd trophic level secondary consumers • carnivores • 4th trophic level tertiary consumers • Top carnivore

42. Trophic levels are shown in diagrams called energy pyramids • The pyramid is only 4 levels high • Energy is lost between each successive level • 10% rule • Example • If herbivores eat 1,000kg of plant material, only 100kg is converted into usable energy • Carnivores that eat the herbivore only gain 10kg of usable energy • Top carnivores only gain 1kg of usable energy Target #29- I can describe how energy moves through the trophic levels

44. Population Ecology Ch. 34.3- Global Biogeochemical Cycles

45. Target #30- I can define biogeochemical cycleTarget #31- I can describe the general steps involved with a biogeochemical cycle • Biogeochemical cycles: the pathways by which chemicals circulate through ecosystems • Involves the following items • Reservoir: a source normally unavailable to producers, like fossilized remains • Exchange pool: a source from which organisms generally take chemicals, like the atmosphere or soil • Biotic community: how chemicals move along food chains

46. Target #32- I can state how matter moves through the water, phosphorus, nitrogen, and carbon cycles using a diagram