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Chapter 6

Chapter 6. Populations. Population Properties. The numbers or population of an organism is limited by their environment Population - all the members of a species living in the same area at the same time Ex: all the oak trees in Houston County. Properties. Can be described by :

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Chapter 6

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  1. Chapter 6 Populations

  2. Population Properties • The numbers or population of an organism is limited by their environment • Population- all the members of a species living in the same area at the same time • Ex: all the oak trees in Houston County

  3. Properties • Can be described by: • Population size • Population Density • Patterns of dispersion • Demographics • Population growth • Limits on population growth

  4. Terms to Know • Population size- number of individuals present living in a defined area • Population Density- number of individuals in a population per unit area • Population dispersion or distribution- the spatial arrangement of organisms within a particular area • Sex ratio- proportion of males to females

  5. Distribution Patterns • Populations may be distributed in different ways: • 1. Random- individuals located haphazardly in no particular pattern (minimal interaction) • Individuals are independent of others • Can occur when resources are found throughout an area

  6. Distributions • 2. UNIFORM DISTRIBUTION • Individuals are evenly spaced, same distance apart • Can occur when individuals hold territories or compete for space • Ex: plants in the desert need certain amount of “root” space to get water they need

  7. Distributions • 3. CLUMPED DISTRIBUTION • Most common in nature • Organisms arrange themselves according to the availability of resources • Organisms interact and are attracted to certain areas • Ex: Bees and flowering plants, breeding pools, humans to urban areas

  8. Distribution Patterns

  9. Age Distribution/Structure • Describes the relative numbers of organisms of each age within a population • Can make predictions based on age structure • Ex: Population past reproductive age will decline over time • Population pre-age or at age of reproduction- will likely increase • Even age distribution – remain stable

  10. Age Structure Diagrams • Survivorship: percent of members likely to survive • Growth rate: birth & death rates, change in size • Growth rate= birth rate – death rate • Rate can be zero (no increase); negative (decrease); or positive (exceeds death rate)

  11. Age Structure Diagram

  12. Graphs

  13. Survivorship Factors • Determined by 4 factors: • 1.) Births (natality) • 2.) Deaths (mortality) • 3.) Immigration– arrival on individuals outside the population • 4.) Emigration– departure of individual from the population

  14. Survivorship Types K-selected r-selected Devote their energy and resources to producing as many offspring as possible in a short time Survivorship is left to chance Exponential Growth • Devote large amounts of energy and resources to caring for a few offspring • Tend to stabilize over time at or near their Carrying Capacity • K is abbreviation for Carrying Capacity

  15. Exponential Growth • Occurs when a population or anything else, increases by a fixed percentage each year • Occurs when pop. has plenty of food, space and limited competition or predators

  16. Limiting Factors • Restrain population growth • Are: physical, chemical and biological characteristics • Carrying Capacity- the maximum pop. size of a species that a given environment can sustain

  17. Carrying Capacity Graph

  18. r-selected vs K-selected

  19. Exponential vs Logistic

  20. Logistic Growth (Curve)(Carrying Capicity) • limiting factors = environmental resistance • Space, food, water, shelter, disease, predators, temp. mates/breeding sites • Plants: sunlight, moisture, soil • Aquatic: salinity, sunlight, temp, dissolved oxygen, and pollutants

  21. Limits to Pop. Growth • Density Dependent: depends on size of the population • Factors that occur with the size of the population • Increases and decreases with population density • Can help find mates, but increases: • Competition • Predation • Disease and Parasitism

  22. Limits to Pop. Growth • Density Independent • Limiting factors that affect the population regardless of size (density) • Can eliminate large #’s of individuals without regard to their density • Examples: • Climate/Temperature extremes • Natural/Catastrophic events or disasters • Human Activity

  23. Chapter 6: Communities Species Interactions and Community Ecology

  24. Organisms Niche • Includes species habitat use, its role in the community, consumption of foods, use of resources, role in food chain/food web, and it’s interactions with other organisms • Summary of everything an organism does in its environment

  25. Types of Niches • Fundamental Niche • The full niche of a species • No competitors • Fulfills all its roles or uses all resources it can and capable of using • Realized Niche • Plays only a part of its (species) role • Forced to use fewer resources due to competition or other species interactions • Competitors restrict what an organism can do or what resources it can use • Chart – Fig. 6.2, pg. 143

  26. Species Relationships • When 2 organisms living in close association with each other interact = Symbiotic relationship • In symbiosis, at least one of the organisms usually benefits from the relationship

  27. Species Interactions • Types: • Competition • Predation • Parasitism • Herbivory • Mutualism • Commensalism/Amensalism

  28. Competition • Occurs when more than one species is seeking or attempting to use the same limited resource • Can take place in 2 ways: • Intraspecific Competition – competition among members of the same species • Interspecific Competition – competition among members of two or more different species

  29. Consequences of Competition • Competition Exclusion – when one species excludes another species from resource use entirely • Species Coexistence – when neither species fully excludes the other, live in equilibrium; • *use resources at different times of the day or different levels • Resource Partitioning – the species partition or divide the resources they use in common • Character displacement – evolve physical characteristics that reflect their portion of resource use, natural selection; *Ex: birds eat same type of seed – one eats the smaller, the other the larger seeds • Larger seeds = bigger beak; Smaller seeds = smaller beak (Darwin’s Finches)

  30. Predation • Process in which a (predator) hunts, captures, kills, and eats another organism(prey); *one benefits/one harmed • The primary organization forces and influence in community ecology • These interactions structure/influence food chains/webs, community make up, numbers and abundance of the predator and prey; creates cycles in populations

  31. Predation

  32. Adaptations of Predation • Camouflage: blending in with environment • Warning coloration: black stripes or red, orange and yellow • Mimicry: imitates another organisms warning coloration • Protective covering: quills, shells, exoskeleton • Odors/Poisons/Inks: skunks, snakes, octopus • Flying

  33. Parasitism • Relationship in which one organism (parasite) depends on another (host) for nourishment, while doing the host harm • Some parasites cause little harm, while others kill • Some parasites live in close contact with the host; ticks, tapeworm, and lampreys • Others are free-living and come into contact with the host infrequently

  34. Herbivory * When animals feed on the tissues of plants • Insects that feed on plants are the most widespread type • Some plants recruit animals as allies to help in defense

  35. Mutualism • Relationship in which 2 or more species benefits from the interaction with each other • Bacteria in our intestines • Acacia trees and ants – trees provide shelter, the ants defend and protect the trees

  36. Commensalism and Amensalism • Commensalism: one species benefits, the other is neither harmed or helped (unaffected); *Sharks and remora’s: remora’s attach to sharks and feed on scraps of food; clown fish/sea anemome • Amensalism: one species is harmed and the other is neither harmed or helped (unaffected); *Ex: black walnut tree that secretes chemical that kills neighboring plants, penicillin/bacteria

  37. Ecological Communities • Energy passes through Trophic Levels • As organisms feed on one another, energy moves through the community • Producers = 1st level • Primary consumers = 2nd level; herbivores • Secondary consumers = 3rd level; eat primary consumers • Tertiary consumers = 4th and up; eat 2nd and 3rd

  38. Energy/Biomass • Food webs: show relationships and energy flow • Keystone species: strong impact on community; secondary and tertiary consumers • Community that resists change and remains stable; shows resistance • A community that changes in response to disturbance then returns to original state; shows resilience

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