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Chapter 8 Populations.

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Presentation on theme: "Chapter 8 Populations."— Presentation transcript:

1 Chapter 8 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

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 r-selected K-selected
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 Devote their energy and resources to producing as many offspring as possible in a short time Survivorship is left to chance Exponential Growth

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 Anything that Restrain population growth
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)
Plants: sunlight, moisture, soil Aquatic: salinity, sunlight, temp, dissolved oxygen, and pollutants limiting factors = environmental resistance Space, food, water, shelter, disease, predators, temp. mates/breeding sites

21 Limits to Pop. Growth Increases and decreases with population density
Density Dependent: depends on 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 Examples: Density Independent
Climate/Temperat ure extremes Natural/Catastrop hic events or disasters Human Activity Density Independent Limiting factors that affect the population regardless of size (density) Can eliminate large #’s of individuals without regard to their density

23 Chapter 8: Species Interactions
And Community Ecology

24 Standard 3 - Communities
CLE – Ecological niches and various habitats CLE – Species interactions, predation competition = symbiotic relationships

25 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

26 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

27 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

28 Species Interactions Types: Competition Predation Parasitism Herbivory
Mutualism Commensalism/Amensalism

29 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

30 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)

31 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

32 Predation

33 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

34 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

35 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

36 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

37 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

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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