1. Ecology
Ecology is the study of how organisms interact with each other and with their environment
Structure
Function
Structure includes the distribution and abundance of organisms; Function includes how populations grow and interact

2. Ecology Biotic = Living
Examples: Predation, competition, reproduction (mating)
Abiotic = Non-living (Energy & Inorganic)
Examples: Temperature, pH, light, water, nutrients
Others? Biotic: Prey, parasitism, disease
CO2, O2,

3. Levels of Ecological Organization
Populations
Communities
Ecosystems
The nature of the community is determined by…
Combo of genes – a sample of the population’s total genetic information

4. Levels of Ecological Organization: Population
A group of individuals of the same species living together in one area; interbreeding
The nature of the community is determined by…
Combo of genes – a sample of the population’s total genetic information

5. Levels of Ecological Organization: Population
A group of individuals of the same species living together in one area; interbreeding
The nature of the community is determined by…
Combo of genes – a sample of the population’s total genetic information

6. Levels of Ecological Organization: Community
Populations of different species living together in one area; naturally-occurring
(e.g., tide pools, ponds, grassland meadows, forest canopy, fallen log, etc)

7. Levels of Ecological Organization: Ecosystem
Communities and non-living components of the environment in which they interact
Energy and nutrents in one find their way to another, so that ultimately all parts of Earth are interrelated in one whole. E.g. stream ecosystem is strongly influenced by the terrestrial ecosystem through which it flows

8. Population Structure Population size – number of individuals
Population density – number of individuals per unit space (area)
Population dispersion – how individuals are distributed
e.g. US census

9. Population Size Number of individuals
Affects population’s ability to survive
Too small – population more likely to go extinct
Too large – increased competition (may be bad for individuals but can lead to natural selection!)

10. Population Density Number of individuals per unit area
Affects population’s ability to survive
Too dense – increased competition (e.g., for resources, food, mates), can lead to reduced fitness, increased potential for disease
Too sparse – can be problematic; must find mates! Also, there is safety in numbers, can lead to increased predation
Alee affect

11. Population Distribution
How individuals are distributed
Nature is patchy!
Differences in light, moisture, temperature, wind, etc. exist within a given ecosystem
Distribution may be random, uniform, or clumped

12. Random
Random – position of each individual is independent of the others
Dispersal depends on resource distribution
Not common in nature
Occurs when individuals do not interact strongly with each other and when they are not affected by nonuniform aspects of their environment; e.g. some species of trees in Panamanian rain forests

13. Uniform Uniform – individuals are evenly spaced
Usually a result of competition for resources
Spacing is frequently accomplished by territorial behavior

14. Uniform
Example: The uniform distribution of cactus resulting from allelopathy
Allelopathy = particular form of interference competition among plants and animals; production and release of chemical substance by one species which inhibits the growth and development of another species; Corals do this too!

15. Clumped Clumped – individuals are aggregated in patches
Occurs frequently in response to uneven distribution of resources
Common in nature
Many advantages
Common because individual animals and plants tend to occur in habitats defined by distinct soil type, moisture, or other aspects of the environment in which they are best adapted

16. Clumped Social interactions may also lead to clumped distribution
Safety in numbers
Shared knowledge of others in group
Decreased energy in movement
Other advantages?
(e.g., flock of birds, herd of bison, pride of lions)
Common because individual animals and plants tend to occur in habitats defined by distinct soil type, moisture, or other aspects of the environment in which they are best adapted

17. Metapopulation
A network of distinct populations that interact with one another by exchanging individuals (immigration and emigration)
May prevent long-term extinction
Source-sink metapopulations – population in better-suited habitats (source) disperse new individuals to populations in poorer habitats (sink)
Marine protected habitats; Whales?
Prevent extinction by colonization of empty patches; dispersal; ex: if one patch experiences an endemic disease, etc

18. Population Dynamics
Survivorship – percentage of original population that survives to a given age
Survivorship Curve – a graphical representation of the survivorship at each age
Depicts age-specific mortality through survivorship
Type I, II, and III

19. Survivorship Curves
Plots the number of individuals of a particular age cohort against time
Compares populations of one area, time, sex, or species with populations of another
Three types of curves: Types I, II, and III

20. Survivorship Curve – Type I
Convex
Typical of populations whose individuals tend to live out their physiological life span (high degree of survival at all ages, but experience heavy mortality at the end of their life span)
Examples – Red Deer, Humans, Annual Phlox (flowering plant)
Plant ornamental, native to southeast US,

22. Survivorship Curve – Type II
Linear
Typical of organisms with constant mortality rates (mortality does not change with increasing or decreasing age)
Examples – adult stages of many birds, rodents and some plants

23. Survivorship Curve – Type III
Concave
Typical of organisms with extremely high mortality in their early stages of life
Examples – many species of invertebrates, fish, some plants

24. Survivorship Curve – Type III

25. Survivorship Curves

26. Population Growth
Populations typically maintain a constant size regardless of how many offspring are born
No matter how rapidly populations may grow, they eventually reach their carrying capacity (K) – the maximum number of individuals that the population can support
Limits include shortages of water, habitat, light, nutrients, etc.

27. Population Growth
The rate of population growth (r) is defined as the difference between the birthrate (b) and the death rate (d) and corrected for the movement of individuals into (i) and out of (e) the population
Population growth (r) = (b - d) + (i – e)

28. Population Growth
Biotic potential – the rate at which the population will increase when no limits are placed on its rate of growth
Defined as: dN/dt = riN
N = number of individuals in the population
dN/dt = the rate of change in its numbers over time
ri = the intrinsic rate of natural increase for the population
(intrinsic = innate, belonging to something by its very nature)

29. Population Growth
Biotic potential is exponential; the rate of increase remains constant, the actual number of individuals accelerates rapidly as the size of the population grows
Result of unchecked exponential growth is a population explosion
Brown tree snake on Guam – eliminated native bird populations; remaining birds extremely patchy in distribution – essentially extinct
Castaway in military cargo after WWII from Papua New Guinea – unsure of exact means; only other snake on the island (native) feeds on termites, does not impact bird or human populations

30. Population Growth
As a population approaches its carrying capacity, its rate of growth slows
Logistic growth equation:
dN/dt = rN ((K – N)/ K)
dN/dt = the growth rate of the population
r = the intrinsic rate of increase
N = the number of individuals present at any given time
(K – N)/K = the unused carrying capacity
Because fewer resources remain for each new individual to use; can be explained by…
The growth rate of the population (dN/dt) is equal to its intrinsic rate of increase (r) multiplied by the number of individuals present at any given time (N), and adjusted for the amount of resources available by multiplying by the fraction of K, the carrying capacity still unused
The growth rate of the population is equal to its intrinsic rate of increase, r, multipled by the number of individuals present at any given time, N, and adjusted for the amount of resources available by multiplying by the fraction, K – the carrying capacity still unused

32. Two Models of Population Growth

34. Human populations exhibit exponential growth
Substantial growth occurred following the industrial revolution (late 1800’s) despite major ‘collapses’ in earlier history
… which significantly lowered the death rate

35. Limits to Population Growth
Resource limitation
Food, Habitat
Predation
Parasitism, Disease
Anthropogenic Impacts – invasive species, habitat destruction, pollution, hunting
How about a little exercise??? 

36. Community Ecology Study of interactions among populations Niche
the functional role of a species in the community, including activities and relationships
total of all the ways an organism uses resources in its environment
Food consumption, space utilization, temperature range, etc
An organisms place and function, not to be confused with Nitzche

37. Fundamental and Realized Niche
Fundamental niche – the entire niche that a species is capable of using, based on its physiological tolerance limits and resource needs
Realized niche – the actual set of environmental conditions, including the presence or absence of other species, in which the species can establish a stable population

38. Community Ecology Habitat Physical location
Provides shelter, food, places of rest
May involve imprinting – a form of associative learning linking individuals to their place of birth or seasonal range

39. Competition
Struggle between organisms to utilize the same resource when the resource is limited
Can occur between species or within species
Especially strong when niches overlap
Can restrict the niche of species (and lead to natural selection…)

40. Competition
Interference competition – physical interactions over access to resources

41. Competition Examples of competition: Fighting to defend territory
Displacing an individual from a particular location
A fraction of individuals obtain all the resources they need; the remaining individuals get less and produce no offspring, or die
Usually aggressive in animals
Shading of vegetation, production of toxins in addition to consumption/use of resources

42. Interspecific Competition
Interspecific competition – occurs when 2 different species attempt to use the same resource, and there is not enough of the resource to satisfy both
Cheetahs and lions for example – niche overlap, lions eat food killed by cheetahs

43. Competition Intraspecific competition – competition within a species
Elephant seal harems, Grasshoppers, trees

45. Competition for niche occupancy
Classic study of barnacles by J.H. Connell
Scotland coast
Semibalanus balanoides inhabits deeper water (lower level of substrate); Chthamalus stellatus inhabits shallower water (higher level of substrate)
S. balanoides not usually exposed to air; C. stellatus frequently exposed to air at low tide
In the deeper zone S. balanoides can always outcompete C. stellatus

46. Competition for niche occupancy
When S. balanoides were removed, C. stellatus was capable of occupying the deeper zone
When C. stellatus was removed, S. balanoides was NOT capable of occupying the shallow-water habitat (exposure to air, higher temperatures)
Functional niche of C. stellatus includes shallow and deeper water
Functional and realized niche of S. stellatus identical
Realized niche of C. stellatus much narrower because can be outcompeted by S. balanoides

47. Competitive Exclusion
Principle of Competitive Exclusion – when two or more species coexist using same resource, one must displace or exclude the other
Hypothetical
Gradients exist within any (shared) habitat; fundamental niches may overlap, but realized niches may differ
Usually detrimental to both species over long term

49. Competition Niche overlap can lead to
Resource partitioning – the differentiation of niches that enables two similar species to coexist within a community
Character displacement – the tendancy for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species
Hereditary changes evolve that bring about resource partitioning

50. Resource Partitioning
Anoles lizards on Caribbean islands
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

51. Character Displacement
Allopatric species – species that do not occur together
Sympatric species – species occur together
Example – Darwin’s finches

52. Character Displacement
Niche overlap drives natural selection!
Brought about by selective effects of competition
Differences among species are accentuated where they co-occur
Can lead to sympatric speciation!

53. Predation
Predation – one living organism serves as a food source for another
Prey evolves defenses, predators evolve adaptations to overcome prey defenses, prey evolves further, and so on….
An arms race ensues (and is in constant motion)

54. Predation Plant defenses against herbivores (and visa versa)
Morphological: thorns, spines, plant hairs
Chemical: Secondary compounds (allelopathy)
Green caterpillars of the cabbage white butterfly; mustard oils protect plant against most herbivores, caterpillars are able to break down the compounds

55. Predation Animal defenses against predators
Behavioral: Fleeing, Hiding, Self-defense, Noises, Mobbing, “Flight or fight”
Physical: Camouflage – cryptic coloration, deceptive markings
Mechanical: includes spines and shells
Chemical: Odors and toxins

56. Behavioral defenses

57. Physical defenses
Physical – Camouflage (Pygmy seahorses)

58. Physical defenses
Physical – Camouflage (Shrimp fish, cryptic frog, walking sticks)

59. Camouflage continued…
Camouflage may occur seasonally (arctic fox, ermine, hare)

60. Physical - Disruptive markings
Add zebra and polar bear

61. The Superstar of them all, the Mimic Octopus!

62. Mechanical defenses

63. Chemical defenses
Chemical – may be incorporated from food they eat (milkweed and monarch butterfly)

64. Predation
Aposematic coloration – warning indicated by coloration, anti-predator adaptation to advertise toxins
Toxins don’t do you any good if you have to get eaten first!
Sometimes warning is of unpalatability, and other times depicts danger
Skunks advertise too!

65. Aposematic coloration

66. Mimicry
Batesian mimicry – a mimicry system in which palatible organisms mimic the morphological characteristics of (an often unrelated) noxious species
Named for Henry Bates; English naturalist who observed many mimics in Amazon
Scarlet king snake – red on black, won’t hurt jack; red on yellow, kill a fellow

67. Mimicry Toxic species must not kill predator
Predator must remember negative encounter and learn from the experience
Mimics must overlap geographically with toxic species
Scarlet king snake – red on black, won’t hurt jack; red on yellow, kill a fellow

68. Mimicry
Monarch and Viceroy butterflies – Monarch caterpillars feed on milkweed (toxic plant); incorporate toxins into body; Viceroy mimics

70. Mimicry
Müllerian mimicry – when two or more unpalatable species resemble each other
All organisms are toxic and converge upon a common morphological warning system
Minimizes losses by predation (predators have memory)

71. Predation Can promote species diversity (drives natural selection)
Predator feeds on superior competitor; most successful organism will be most abundant, predators will often select the most abundant prey, especially in plants
Return of wolves to Yellowstone restored native vegetation, which benefits the elk population!

72. Predation Predation reduces competition
Without predators, sick and weak individuals of the population will survive
May pass on (weak) characteristics to offspring reducing fitness potential of the gene pool

73. Predation
Keystone species – a species that has a disproportionate effect on its environment relative to its abundance
Plays a critical role in its ecosystem by maintaining the structure of the ecological community

74. Predation Keystone species – Sea otter

75. Keystone Species – Sea Otter

76. Coevolution and Interspecific Interactions
Coevolution – reciprocal evolutionary adaptations of two interacting species
When one species evolves, it exerts selective pressure on the other to evolve to continue the interaction
May occur within species – if a female selects a male with an extreme characteristic, selection will fuel development of characteristic – may be detrimental!
Peacock tail