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

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 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