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Flashcards in Mid Lecture Deck (207):
1

5 Main principles of Natural selection

Variation, Overproduction, Adaption, Descent with modification(adaption passed on to generations), Fitness(reproductive)

2

Charles Lyell?

Influenced Darwin by theorizing on the age of the earth and its non-static nature.

3

Darwin Influenced by this persons assessment on the consequences of population under limiting resources.

Thomas Robert Malthus

4

Wrote the book Silent Spring which uncovered the consequences of DDT on insect life and bird eggshells.

Rachel Carson

5

Darwin's Natural selection influenced him

German zoologist Ernst Haeckel(1866)

6

"struggle for existence"

Darwin

7

Trophic level descending from Individual:

Organ Systems, organs, tissues,cells,subcellular components,etc.

8

Populations within an ecosystem interact?

competing for resources
predator-prey
mutually beneficial relationships

9

Larger empty fields that were grazed down, fewer bushes and willow resulting in fewer songbirds, small predators dominated, loss of beavers, bear and berries came back. Resulted from?

Removing keystone predators

10

Population?

A population is a group of individuals of the same species that inhabit a given area
–There is a potential for interbreeding among members of the population
–The population has a spatial boundary

11

Characteristics of a population?

–Density
–Proportion of individuals of various ages and stages –Spacing of individuals
–Birth, death, and movement of individual

12

metapopulation?

population in which members can immigrate and emigrate.
•A metapopulation is a collection of local subpopulations
Studied from conservation biology view
Lower probability of long term extinction because of migration.

13

Modular organism?

the zygote develops into a unit of construction that then produces further, similar modules
–Common in plants
-Ex: Aspen trees

14

Kangaroo?

Three largest kangaroo species in Australia have different distribution s that are closely tied to climate.

15

ecological niche?

requirements of a species, role of species

16

Barnacles along intertidal zone?

adapted to survive dry conditions.

17

Territorality?

may regulate density by excluding some individuals from reproducing

18

Resources strongly affect density?

whether food is a limiting factor or not.

19

Population size?

density X area

20

Sampling methods for plants and sessile animals

–Counting the organisms in a subsample (quadrats

21

Mark-Recapture or Capture-recapture Analysis

N(Population)=M(marked animals){n(individuals in 2nd sample)}/R(recaptured)

22

Age Pyramids

represent the age structure of a population at some period in time.

23

Age Structure

a product of the age-specific patterns of mortality and reproduction.

24

primary sex-ratio

1-1
Varies based on factors such as:
-Male Rivalry
-Predation
Ex: North Sask Caribou 67 Males per 100 Females

25

Dispersal

The movement of individuals directly influences the local density.
Emigration vs. Immigration

26

Passive means of dispersal

Some organism use abiotic factors such as wind, gravity, water, animals.

27

Samaras?

Means of passive dispersal using "helicopter" rotors transport seed in air.

28

Philopatric

are individuals that habitually return to the same location, or stay in place

29

Dispersal is active for?

Mobile animals that usually move to find vacant habitat to occupy.

30

Migration?

Round trip with animals returning to original jump of spot.
Can be daily, seasonal, long or short range.

31

Population Growth

refers to how the number of individuals in a population increases or decreases with time
–Individuals added via birth and immigration –Individuals removed via death and emigration

32

Immigration and emigration can only occur in an _____ population

open not closed

33

Birth and Death Rates basic formula?

N(t+1) = N(t) + B(t)-D(t)

•Population size at a particular time = N(t) •The number of hydra reproducing [B(t)] or dying [D(t)] over a particular time period. •The population size (N) at the next time period (t+ 1) would be

•N refers to change in population size
•t refers to change in time (e.g., 1 year, 3.6 days

34

-b
-d

=the proportion of hydra producing a new individual per unit time
=the proportion of hydra dying per unit of time

35

Exponential Growth

The pattern of population size is continuous function of time
–change in population (N) over time (t)
N/t= (b–d)N(t)

36

Rate of change

Rate of change is best described by the derivative of the equation = dN/dt= (b–d)N –This derivative expresses that t approaches zero and the rate of change is instantaneous

37

Per capita rate of increase

r= (b–d) = instantaneous(per capita) rates of birth and death (growth)

38

Exponential population growth

= dN/dt= rN

39

intrinsic natural rate of increase

(maximum rfor a species)sometimes indicated by rm(Malthusian parameter), or rmax

40

r= 0

there is no change in population size

41

r>0

the population increases exponentially

42

r<0

the population decreases exponentially

43

r strategists

Species that live in environments that do not often exist at population carrying capacity = ‘r-selected species

(e.g., random weather events play a large role in determining no. of individuals who survive)

44

k strategists

Species that experience competition, live in populations that do reach ‘carrying capacity’ = ‘K-selected species

(e.g., black bears in a forest, which often have to compete for limited food resources)

45

Geometric Growth

Geometric growth is used to describe growth over discrete time intervals

Appropriate for species that exhibit discrete steps in population growth –E.g., there is a distinct “season of births

46

Life Table

A life table is an age-specific account of mortality

x= age classes

nᵪ= the number of individuals from the original cohorts that are alive at the specified age (x)

–lx= the probability at birth of surviving to any given age (x)

-dx= the difference between the number of individuals alive for any age class (nᵪ) and the next older age class (nᵪ+ 1 )

–qx= age-specific mortality rate, the number of individuals that died in a given time interval (dx) divided by the number alive at the beginning of that interval (nx)

ex= age-specific life expectancy, the average number of years that an individual of a given age (nx) is expected to live into the future

47

cohort

is a group of individuals born in the same period of time

48

Life Expectency

ex= age-specific life expectancy, the average number of years that an individual of a given age (nx) is expected to live into the future
ex= T(x)/N(x)

Lx= the average number of individuals alive during the age interval xto x+ 1. –Assumes mortality is evenly spread over the year

Tx= the total years lived into the future by individuals of age class xin the population

49

crude birthrate

The crude birth rate is expressed as births per 1000 individuals in a population per unit time
–Only females give birth
–Birthrate of females generally varies with age
•Birthrate is better expressed as the number of births per female of age x

bx= mean number of females born to a female in each age group –Continuing with the gray squirrel exampl

50

gross reproductive rate

= gross reproductive rate, the average number of female offspring born to a female over her lifetime

51

net reproductive rate

R0= net reproductive rate, the average number of females that will be produced during a lifetime by a newborn female
lx (x) bx

52

fecundity tables

•A fecundity tablecombines the survivorship (lx) with the age-specific birthrates (bx)
•lxbx= mean number of females born in each age group, adjusted for survivorship

53

generation time

is defined as the mean time between when female is born and when she reproduces

•Generation time (Tc) is approximated as the mean age of reproducing individuals
-Summing the lengths of time to reproduction for the entire cohort, divided by the total offspring



54

Generation time finding r

•Taking the natural logarithm of both sides we can express r as

r ~ ln(R0)/ Tc

•For the grey squirrel cohort r~ ln(1.4)/1.88 = 0.18

55

S shaped model

•No population has indefinite growth
•Often limits are imposed by the environment
•As population densities increase, interactions intensify, resulting in regulated growth
•Logistic growth is a S-shaped model in which birth and death rates vary in a density-dependent manner

56

Exponential Growth vs. Logistic

•Exponential growth makes two assumptions: 1.Essential resources (e.g., space and food) are unlimited
2.Environment is constant
•Under these assumptions birth and death rates are constant
•The natural intrinsic rate of increase (rm) is fully realized

•In the real world, neither assumption holds
•Resources are limited and environments are variable
•As population densities increase, demand for resources also increases
•If the rate of consumption exceeds the rate at which resources are resupplied, then resources will shrink
•Shrinking resources increase mortality (death) rates, and decrease fecundity (birth) rates
•This represents a significant departure from the expectations of a exponential growth model

57

10.7 Logistic growth # 13 remember equation in black= September 21 and 23

dN/dt= rNN K ()

58

oscillation

movement back and forth at a regular speed.

59

r- max predicts

the types of cycles

60

prairie parkland

most endangered area in Canada < 3% left

61

The Allee effect

The Allee effect is the decline in reproduction or survival under conditions of low population density

Ex: Ethiopian Wolf
ex: Passenger Pidgeon

62

Mutualistic Symbiosis or Mutualism

–is an interspecific interaction that benefits both species
Ex: Plant-pollinator

63

Detritivory

•Important for nutrient cycling and community dynamics

64

Interspecific Competition

One of the most important drivers of natural selection

Interspecific competition is a relationship that affects the populations of two or more species adversely

–Exploitation competition occurs when species indirectly interact with one another but affect the availability of shared resources
–Interference competition results when species directly interact and prevent others from occupying a habitat or accessing resources within it

65

Intraspecific competition

–Intraspecific competition is the same relationship but occurs among individuals of the same species

66

complete competitors

are two species that live in the same place and have exactly the same ecological requirements

67

niche(n dimension hypervolume)

A species-defined “space” where it can survive, grow and/or reproduce is in response to n-dimensional environmental factors •Niche dimension include resources(e.g., food, habitat and light, etc.) and conditions(e.g., temperature, humidity, pH, etc.)

68

George Evelyn Hutchinson

was an AngloAmerican zoologist known for his studies of freshwater lakes and considered the father of American limnology. He popularized the niche concept and character displacement.

69

ecology

is the scientific study of the relationships between organisms and their environment

70

environment

–External factors that influence survival, growth and/or reproduction
–Abiotic habitat and biotic interactions

71

relationships

–Interactions with physical aspects of environment –Interactions with same and other species

72

conditions

can influence an organism but can not be consumed (e.g., temperature, day length, or acidity), including some hazards

73

resources

can be consumed thus making them less available for others (e.g., food, water, and mates)

74

Ernst Haekel

German zoologist Ernst Haeckel in 1866 coined the term Ecology –Derived from the Greek oikos meaning house

75

Haeckel’s formal definition of ecology was rooted in the _____ concept of the “struggle for existence” .

Darwinian

–Darwin’s theory of natural selection was a critical cornerstone for the emergence of ecology as a science

76

7 levels of the Ecological Hierarchy

–Individual •Organ systems, organs, tissues, cells, subcellular components, etc.
–Population
–Community
–Ecosystem
–Landscape
–Biome
–Biosphere

77

community

A community includes all populations of different species interacting within an ecosystem

78

Landscape

The landscape is the area of land (or water) that is composed of different communities and ecosystems –At this level, communities and ecosystems are linked by the dispersal of organisms and the exchange of materials

79

Biomes

Biomes are geographic regions with similar geological and climatic conditions –For example, boreal forest, aspen parkland, grasslands

80

Biosphere

•The biosphere is the thin layer surrounding the Earth that supports all of life

81

Global Abiotic Factors

(1) atmosphere, (2) hydrosphere, (3) lithosphere

82

Ecologists ask different questions and are interested in different patterns at different ecological levels=

Name the 8 levels and describe what ecologists look for in each

-Individual: discrete birth and death events

-Population: rates of birth and death, distribution of individuals

-Community: factors that influence the relative abundance of a species

-Ecosystem: flow of energy and nutrients through the physical and biological systems

–Landscape: factors that influence the spatial distribution of ecosystems and the effect on organisms

–Biome: patterns of biological diversity with geography

–Biosphere: interactions between ecosystems and atmosphere

-Global ecology studies how the exchange of energy and matter between ecosystems and the atmosphere, hydrosphere, and lithosphere influences global conditions

83

Steps in scientific method

–Make an observation; if something cannot be observed, it cannot be studied by science
•Requires replication (to minimize bias)
•Observational stage is prolonged and complex
•Experimentation not involved
•Multivariate measurement and analysis

–Form a question: to seek an explanation of the observation using one or more propositions (i.e., mechanisms or processes)

–Hypothesis generation: to generate a proposed explanation to the question
•Guided by research experience
•Explanation must be a testable cause and effect statement
•Leads to predictions

–Make a prediction: based on the hypothesis, what you expect to discover under certain conditions

–Hypothesis testing: gather data (nonexperimental approach) to determine if they agree with predictions
•If they agree --> method is repeated to expand the scope of the problem investigated
•If they do not agree --> a new hypothesis must be constructed and tested

84

Example of use of scientific method

Sable Island horses and grey seals

85

field study

In a field study, an ecologist examines natural patterns across the landscape
–The relationship between two or more variables is studied
–The results suggest a relationship but do not prove cause and effect

86

experiment

In an experiment, an ecologist will test under controlled conditions and controls the independent variable in a predetermined way
–Required in order to determine cause and effect –Two experimental approaches are possible

87

field experiment

In a field experiment, the test is applied in a natural setting
–In this type of experiment, it is difficult to control other influencing factors
–Results are realistic because they are collected from a natural setting

88

Lab Experiment

In a laboratory experiment, the ecologist has much more control over abiotic factors –Results are not directly applicable in the field

89

Reiteration

•Reiteration or repetition is required in order to achieve consistency in results
–Lack of consistency may result from small sample sizes

90

Natural Experiments

Natural experiments are not true experiments in a scientific sense (may not use the rigorous steps just outlined)
–Often employed to monitor response to natural disturbance (i.e., fire) or another event
–No manipulation of treatments
–Controls are often defined as similar affected areas –Valuable for hypothesis generation and observation of impacts that would otherwise not be possible given the scale of observation

91

Models(2)

–Are abstract, simplified representations of real systems –Allow us to predict behaviour or response

–Can be mathematical(quantitative predictions) or verbal(qualitative statement where the magnitude of prediction is not possible)

92

Life History Characteristics

Life history characteristics: traits that affect and are reflected in the life table of an organism

93

Life History

Life history: the lifetime pattern of growth, development, and reproduction

94

Monogamy

Monogamy involves pair bonds between one female and one male (both care for offspring)

95

Polygamy 2 types

Polygamy involves an individual (male or female) having more than one mate
–Polygyny: single male mates with many females –Polyandry: single female mates with many males

96

Polyandry

–Polyandry: single female mates with many males

97

Polygyny

Polygyny: single male mates with many females

98

Promiscuity

Promiscuity is defined by individuals (male or female) who mate with many individuals (i.e., no pair bonds are formed)

99

Monogamy explained

Monogamy exists mostly in species where parental cooperation is critical
–Most common in birds
–Least common in mammals (only 5% of mammal species are monogamous)
–North American examples include:
•Carnivores such as foxes and weasels (Mustela spp.)
•Herbivores such as beavers (Castor spp.), muskrats (Ondatrazibethica), and voles (Microtus ochrogaster)

Within primate species, monogamy is more common (15%)
–The gibbon (Hylobatesspp.) is the only large primate that is monogamous –In humans, monogamy is not universal

100

Polygyny explained

Polygyny is very common among mammals
–The size of the harem is a result of the extent and synchronicity of female sexual receptivity
•If females are sexually active over a short period of time (synchronous), harem size is limited to small groups (e.g., white-tailed deer)
•If females are receptive over a long period of time (non-synchronous), harem size will be large (e.g., elk [Cervuselaphus])
•Over very long periods of time…small harems that last year round (e.g., horses, gorillas)

Polyandry (one female and more than one male)is known in only three bird groups
–The jacanas (Jacanidae)
–The phalaropes (Phalaropusspp.)
–The sandpipers (Scolopacidae)

101

Intrasexual selection

Intrasexual selection involves same-sex competition among polyandrous species (i.e., male-to-male or female-to-female)
•Promotes aggressive physical and behavioural traits –Examples include large body size, antlers and horns

102

Intersexual selection

Intersexual selection involves differential attractive traits
–Intersexual selection can be antagonistic
•Phenotypic traits may include bright colours or elaborate plumage (ornamentation) display as well as intrasexual characteristics

103

Assortative mating

Assortative mating results when females select mates based on phenotypic “attractive”traits

104

ornamentation

Phenotypic traits may include bright colours or elaborate plumage.

105

Ornate displays in plumage, horns, size or colour confounded Darwin –Requires investment in resources and increases ___ ____ _____.

risk of predation

Ornate displays in plumage, horns, size or colour confounded Darwin
–Requires investment in resources and increases risk from predation

106

Swordtails ex

example of sexual dimorphism

Males have a colourful, elongated appendage off the caudal fin (“sword”)
•Females prefer males with long appendages

107

How are Polygynous vs Polyandrous populations affected by sexual selection

In polygynous populations, selection is more intense for males
•Fewer females increase competition among males
•Engaging in multiple mating may decrease female fitness (increasing exposure to disease and predation)

In polyandrous populations, sexual selection becomes more intense among females

108

Reproductive effort

Reproductive effort is the time and energy allocated for reproduction
–Trade-offs: if more energy allocated to reproduction, less will be available for maintenance, growth, and defence
•There is a negative relationship between growth and reproductive effort
–Examples, wood lice (Armadillidiumvulgare) and Douglas-fir (Pseudotsugamenziesii)

109

There is a _____ relationship between growth and reproductive effort.

negative

110

Natural selection favours individuals that produce the maximum number of ______ offspring in a lifetime

reproducing

111

Life history depends on

•Degree of parental care and investment
•Age at first reproduction
•Longevity •# offspring per reprdevent
•Size of offspring at birth
•Gender allocation
•Habitat

112

Reproductive Investments= 3

Reproductive investment includes:
–Care
–Nourishment
–Physiological costs of producing offspring
•These costs reduce an organism’s fitness as well as the number of offspring that survive and reproduce

113

Number of offspring produced is decided by=

•There is a trade-off between the number of offspring and their size
–More offspring, the smaller the size of each
•Under unpredictable or disturbed environments, increasing allocation of offspring number increases the odds that at least a few will survive
•Parents that have fewer offspring invest more in each

114

Precocial

active, mobile at birth

115

Altricial

helpless, naked, blind, require more help from mother at birth

116

semelparous and ex

Invest all into growing up to reproduce once in a suicidal effort (die after)

ex: Annual Plants

117

Iteroparous

Spend energy on reproduction in bouts over the lifetime
. Trade-off is in when to reproduce...early or late
E.g. Migratory species: Humpback Whale

118

When to reproduce?

High rates of adult mortality select for early age at first reproduction and vice versa

119

Antagonistic pleiotropy

is when one gene controls for more than one trait where at least one of these traits is beneficial to the organism's fitness and at least one is detrimental to the organism's fitness

120

r strategists

Species that live in environments that do not often exist at population carrying capacity
= ‘r-selected species’

121

K strategists

Species that experience competition, live in populations that do reach ‘carrying capacity’ = ‘K-selected species’

122

r strategists:

1. Potential of population growth=___

2. Competitive ability=____

3. Development=____

4. reproduction=_____

5. type of reproduction=_____

6. body size=______

7. offspring=_____

1. high

2. Not strongly favoured

3. Rapid

4. Early

5. single semelparity

6. small

7. many, small

123

K strategists:

1. Potential of population growth=___

2. Competitive ability=____

3. Development=____

4. reproduction=_____

5. type of reproduction=_____

6. body size=______

7. offspring=_____

1. Low

2. Highly favoured

3.slow

4. Late

5. repeated iteroparity

6. Large

7. Few, Large

124

Zygote grows into a ____ _____ ______.

Genetically unique organism

125

genet

A genet is a genetic individual arising from a zygote

126

ramet

Modules produced asexually by the genet are ramets –Ramets may be physically linked to the parent or separate
–Ramets are clones or exact copies of the parent genet

127

distribution

of a population describes its spatial location and is based on the presence or absence of individuals –Influenced by the occurrence of suitable environmental conditions

128

geographic range

is the area that encompasses all individuals of a species

•Individuals are not distributed evenly throughout the geographic range of a population
•Individuals can only occupy areas that can meet their requirements –or are forced there, due to competition, predation, etc.

129

Abundance= defined

is a function of _______

Abundance is the number of individuals in the population and defines its size
•Abundance is a function of:
–Population density, or the number of individuals per unit area or per unit volume
–The area over which the population is distributed

130

Ecological density

Ecological density reflects the number of individuals per unit of available living space

131

Three population distribution patterns?

•There are three population distribution patterns –Random: an individual’s position is independent of others
–Uniform: results from negative interaction among individuals
–Clumped: results from patchyresources, social groupings, rametdynamic

132

Population size= _____X_______

density, area

–In most cases, population density must be estimated by sampling a portion of the population

•Sampling methods for plants and sessile animals –Counting the organisms in a subsample (quadrats)

133

Capture-recapture or mark-recapture

–Capture-recapture or mark-recapture methods are based on trapping, marking, and releasing a known number of marked animals (M) into the population (N)

–Some time later, the same population is sampled and the ratio of marked (R) to sampled (n) individuals in the second sample represents the ratio for the entire population

134

Capture-recapture or mark-recapture ex problem

E.g., Capture 80 butterflies, mark, release, recapture 120, of which 40 are marked. What is estimated N?

N=Mn/R

80X120
_______
40

= 240

135

primary sex ratio=

1:1

136

One way movement of individuals(2)

–Emigration is when an individual moves out of a subpopulation
–Immigration is when an individual moves into a subpopulation

137

passive dispersal

means of dispersal
—gravity, wind, water, animals
–The dispersal distance depends on the agents of dispersal

138

Philopatric

Philopatric are individuals that habitually return to the same location, or stay in place

139

Migration

•Migration is a round-trip movement made by an animal
•Migrations may be daily or seasonal, short or long range

140

Life table data are generally presented as: 2

- Mortality curve(that plots the qx column against age (x)

- Survivorship curve(that plots the lxcolumn against age (x)

Life tables and curves are based on data from one population at a specific time and under certain environmental conditions

141

Three types of survivorship curves

–Type I: typical of populations in which individuals have long life spans, survival rate is high throughout the life span with heavy mortality at the end
•Humans, other mammals, some plants

–Type II: survival rates do not vary with age
•Adult birds, rodents, reptiles, perennial plants

–Type III: mortality rates are extremely high in early life
•Fish, many invertebrates, and plant

142

demography

study of population growth

143

The crude birthrate is expressed as births per _____ individuals in a population per unit time

1000

–Only females give birth
–Birthrate of females generally varies with age

144

bx

bx= mean number of females born to a female in each age group
–Continuing with the gray squirrel example

145

R0=1
R0<1
RO>1

•R0=1; on average, females will replace themselves in the population
•R0<1; females are not replacing themselves in the population
•R0>1; females are more than replacing themselves in the population

146

Logistic growth(s shaped)

•No population has indefinite growth
•Often limits are imposed by the environment
•As population densities increase, interactions intensify, resulting in regulated growth
•Logistic growth is a S-shaped model in which birth and death rates vary in a density-dependent manner

•In the real world, neither assumption holds
•Resources are limited and environments are variable
•As population densities increase, demand for resources also increases
•If the rate of consumption exceeds the rate at which resources are resupplied, then resources will shrink
•Shrinking resources increase mortality (death) rates, and decrease fecundity (birth) rates
•This represents a significant departure from the expectations of a exponential growth model

147

Exponential growth assumes two things

Exponential growth makes two assumptions:
1.Essential resources (e.g., space and food) are unlimited
2.Environment is constant

148

Logic Equation population modelling

b>d
b

–When b> d rate of population growth (dN/dt) increases
–When b< d rate of population growth (dN/dt) decreases
–When b= d the rate of population growth (dN/dt) =0

149

The population size when b= dis called the _____ ______

carrying capacity

150

World population began accelerating about _____ to _____ years ago and has “exploded” in the past 1 000 years

10-12000

151

3 surges in human population= causes?

1. Invention of tools and clothes and fire
2. Agricultural Rev
3. Industrial Rev

152

estimated world pop by 2100?

10.9 billion

153

density-dependant effects

Density-dependent effects influence a population in proportion to its size

154

Mechanisms of density-dependence

Mechanisms of density-dependent population regulation (birth and death rates) include:
–Resource availability
–Patterns of predation
–Spread of disease or parasites
–Allee effect (inverse density dependence)

155

Competition

Competition occurs when individuals use a common resource that is in short supply relative to the number seeking it

156

intraspecific competition

Intraspecific competition occurs among individuals of the same species

157

When resources are scarce, a population may respond in one of two ways?

Scramble competition occurs when growth and reproduction are depressed equally across individuals as competition intensity increases

–Contest competition takes place when some individuals claim enough resources while denying others a share

158

result of scramble competition?

Scramble competition can result in local extinction if all individuals receive insufficient resources (this is the extreme case)

159

result of contest competition

Only a fraction of the population may suffer in contest competition
—those that access resources function to sustain the population

160

Exploitation competition

Exploitation competition occurs when individuals indirectly interact with one another but affect the availability of shared resources (e.g., herbivores on the African savannas)

161

Interference competition

Interference competition results when individuals directly interact and prevent others from occupying a habitat or accessing resources within it (e.g., bird species’ nesting sites)

162

The intensity of intraspecific competition is usually _____ ______ and increases gradually

The intensity of intraspecific competition is usually density dependent and increases gradually
–Initially affects growth and development
–Later affects individual survival and reproduction

163

Density-dependant growth

Density-dependent growth is the inverse relationship (observed in many species) between population density and individual growth

164

self thinning

Self-thinning is the progressive decline in density and increase in growth (biomass) of remaining individuals caused by:
–Density-dependent mortality
–Population growth

165

Competition can affect fecundity and ex

Competition can reduce fecundity
•Sexual maturity in harp seals (Phoca groenlandica) is directly related to body weight
–Reduced growth rates (weight gain) under high population densities increase the mean age at which females become reproductive
–Harp seal fertility (the number of females giving birth to young) is density dependent

166

density-independent factors and ex

Density-independent factors are those that may influence birth and death rates of a population but do not regulate population growth
–Temperature
–Precipitation
–Natural disasters

ex=
•Outbreaks of spruce budworm (Choristoneura fumiferana) are correlated with drought
•Kangaroo rat (Dipodomys merriami) reproduction is stimulated by plant growth (which is stimulated by fall rains)
•Accumulation of snow affects white-tailed deer population dynamics
–The average number of fawns/doe and subsequent annual change in population is inversely related to the previous winter’s snow accumulation

167

key ecological concepts related to species interactions

Key ecological concepts related to species interactions:
1.Individuals of different species that coexist in a community interact in different ways
2.Traits that allow these interactions are adaptations, phenotypic traits resulting from natural selection

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Mutualism and ex

Mutualistic symbiosis, or mutualism
–is an interspecific interaction that benefits both species

ex: Insects pollinating may be important drivers of plant population dynamics

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Detritivory important for...

nutrient cycling and community dynamics

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Charles Darwin based his idea of natural selection on competition, the “___ __ _____"

Charles Darwin based his idea of natural selection on competition, the “struggle for existence”
•Adaptations avoid this “struggle” or minimize its effects
•Competition is regarded as the major force behind species divergence and specialization

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Interspecific competition definition and two forms:

Interspecific competition is a relationship that affects the populations of two or more species adversely

–Exploitation competition occurs when species indirectly interact with one another but affect the availability of shared resources
–Interference competition results when species directly interact and prevent others from occupying a habitat or accessing resources within it

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Interspecific competition ex: Paramecium

P. aurelia has a higher rate of population growth than P. caudatum
–When raised together in a test tube on a fixed amount of bacterial food, P. caudatumdied out.

When P. caudatum(the previous experiment’s “loser”) was reared with P. bursaria, they coexisted!
–Each species fed on bacteria in different parts of the test tube

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Ex: D. Tilman studying two Diatom species

•D. Tilman studied the competitive interactions between two diatom species under conditions where silica in the water was plentiful and when it was limiting
•Silica was kept at a low level when each species (Asterionella formosa andSynedra ulna) was grown alone
•When the species were grown together, the use of silica by S. ulna reduced the silica level to below that necessary for A. formosa to survive and reproduce

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Competitive exclusion principle defined

_____ _______ cannot coexist!

•The competitive exclusion principle states that “complete competitors” cannot coexist
–Complete competitors are two species that live in the same place and have exactly the same ecological requirements
•If population of complete competitor A increases the least bit faster than complete competitor population B, then A will eventually outcompete B (B will become extinct)

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n-dimensional hypervolume

G. E. Hutchinson (1957) described the niche as an n-dimensional hypervolume
–A species-defined “space” where it can survive, grow and/or reproduce is in response to n-dimensional environmental factors
–Niche dimension include resources(e.g., food, habitat and light, etc.) and conditions(e.g., temperature, humidity, pH, etc.)

•Hutchinson’s niche concept is often depicted as a three-dimensional space
•Space is not exclusively physical (e.g., habitat) but may include non-physical factors such as light, pH, temperature
•Thus a single habitat may support a number of niches

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Limitation of Hutchinson's concept

•Two species which overlap along a single niche dimension (e.g., temperature) may not interact at higher dimensions (humidity and food size)
•The limitation of Huchinson’s concept is that the number of niche dimensions defined is theoretically limitless
–Thus limiting testability of multiple niche dimensions

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Charles Elton niche concept

•Charles Elton introduced an alternative definition of the niche
•Elton emphasized that species-environment interactions are two-sided:
–A species has an effect on its environment as much or more than its response to its environment

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Two types of niche and ex

•To understand niche and competition we need to distinguish two types of niche:
–Fundamental niche
–Realized niche

ex=

For example, the spatial distribution of two cattail species is partitioned along a water depth gradient –Wide-leaved cattail (Typha latifolia) dominates shallow waters
–Narrow-leaved cattail (T. angustifolia) dominates deeper water

•When grown alone, the fundamental niche of both species is similar (both can survive in shallow water)
•When grown together, the realized niche changes –Typha latifolia outcompetes T. angustifoliain shallow water

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fundamental niche

A species’ fundamental niche is the full range of conditions and resources under which it can survive and reproduce

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realized niche

The realized niche is the portion of the fundamental niche that the species actually exploits

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niche overlap

Competition may intensity if species use the same portion (niche overlap) of a resource space (e.g., habitat, food, or light)

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competition may be reduced if the common resource is partitioned over ______.

Competition may be reduced if the common resource is partitioned over time

–Example, in southern France four weevil species (Curculiospp.) share a common food resource (acorns) –Exploitation of acorns among the four species is temporally separated over a three-month period

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Niche differentiation

•Coexistence of competitors is associated with some degree of niche differentiation
–Niche differentiation: differences in the range of resources used or environmental tolerances

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resource partitioning

•Similar species coexist by partitioning available resources (resource partitioning)
–Different kinds/sizes of food
–Feeding at different times
–Foraging in different areas
–Exploiting the portion of resources unavailable to others

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Resource partitioning...wild cat example

•T. Dayan (Tel Aviv University) examined resource partitioning in a group of wild cat species of the Middle East
–There is a general relationship between the size of canine teeth and prey species selected
–There is a systematic difference in canine size between male and female and among the three coexisting cat specie

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character displacement

Character displacement involves a shift in feeding niche that subsequently affects a species’ morphology, behaviour, or physiology

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“ghost of competition past”

Differences among species have evolved over a long period of time, and we have limited information about the resources and potential competitors that may have influenced natural selection

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Evolutionary affects on resource partitioning ex

•Two finch species (Geospiza fortis and G. fuliginosa) feed on seeds with an overlapping seed size range
•On Santa Cruz island, where the two species overlap, their beak size distribution and hence their seed size selection do not overlap
–Thus reducing competitive interaction
•Seed size and beak size overlap only occurs in regions where the two species do not coexist

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categories of heterotrophic organisms

carnivore, omnivore, herbivore

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classifications of predators(5)

–True predator
–Grazer/browser
–Seed predator/planktivore
–Parasite
–Parasitoid

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functional response

The relationship between the per capita rate of consumption and the number of prey is the predator’s functional response
The greater the number of prey, the more the predator eats

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numerical response and ex

An increased consumption of prey results in an increase in predator reproduction, and this is the predator’s numerical response

•The ability of a predator population to regulate a prey population is related to the response of predators to aggregate
–Predator populations grow slowly in comparison to those of their prey

ex=
•F. Messier examined the complex predator-prey relationship between moose (Alcesalces) and wolves (Canislupis)
•Results from 27 studies suggest that at low moose densities predation is density-dependent
–Moose are solitary, non-migratory herbivores
–Their size makes them more conspicuous
•At high densities moose mortality is regulated by other factors (e.g., bear predation on moose calves)

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Sigmodial type 3 response caused by :

•There are several possible explanations for a sigmoidal type III response:
–Availability of cover: the susceptibility of prey individuals will increase as the population grows and hiding places become filled
–Search image: the ability of a predator to recognize a prey species will increase as the prey population size increases
–Prey switching: the act of a predator turning to a more abundant (but maybe less preferred or palatable), alternate prey

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Keystone species ex:

Key: Starfish
Barnacles and Mussels(dominant)
-When starfish is removed then the mussels take over utilizing the competitive exclusion principle
-starfish allow coexistence of competitors
-Starfish are picky–they prefer mussels (dominant competitor), which allows barnacles (weaker competitor) to coexist.

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Apparent competition

•Predators can also play a role in what is called “Apparent Competition”
–An interaction between to prey species, where the presence of one prey has a negative effect on the other, but not the other way around
–E.g., when one species has a negative effect on another by bringing to it exposure to a pathogen or predator

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Coevolution

Coevolution: as prey species evolve ways to avoid being caught, predators evolve more effective means to capture them

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Red Queen hypo

•The Red Queen hypothesis(V. Valen)
–“Now, here you see, it takes all the running you can do, to keep in the same place.” (Red Queen, Through the Looking Glass)
•For prey to avoid extinction at the hands of predators, they must evolve means of avoiding capture

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Prey defense types: 6

•Predator defences are the wide range of characteristics to avoid being detected, selected, and captured by predators:
–Chemical defences
–Colouration
–Mimicry
–Structural defences
–Behavioural defences
–Reproductive traits

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Chemical Defence

•Chemical defence is widespread
–Alarm pheromones induce flight reactions in members of the same and related species
–Odorous secretions repel predators
–Storage or synthesis of toxins and poison

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Colouration defence

•Cryptic colouration includes colours and patterns that allow prey to blend into the background
•Object resemblance common among insects
•Flashing colouration may distract and disorient predators or it may serve as a signal to promote group cohesion

•Animals that are toxic to predators or use other chemical defences often possess warning colouration or aposematism
—these are bold colour patterns that serve to warn would-be predators

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aposematism

warning colouration

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Batesian Mimicry

•Batesian mimicry occurs when an edible species mimics the inedible species (the model)
–Butterflies and snakes
–Mimicry is not limited to colour pattern (e.g., rattle-like sound)

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Mullerian mimicry

•Müllerian mimicry is the similar colour pattern shared by many unpalatable or venomous species –This is effective because the predator has to be exposed to only one of the species before learning to stay away from all other species with the same warning colour patterns

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Structural defence

•Protective armor(shells, quills) is used by some animals for defence

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Behavioural defences

•A wide range of behavioural defences is known to help prey avoid or escape predators
–Change foraging behaviour
–Alarm calls
–Distraction displays
–Living in groups
–Predator satiation: most of the offspring are produced in a short period of time

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predator satiation

most of the offspring are produced in a short period of time

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Plant defence

Plants employ both structural and other defences against herbivory:
1.Structural defences such as hairy leaves, thorns, and spines can discourage feeding
–The cellulose and lignin content make most plant tissues a low-quality food

2.Chemical defences are the main line of plant defence
•Secondary metabolites are chemicals produced by plants that either reduce the ability of herbivores to digest plant tissue or deter herbivores from feeding –Nitrogen-based compounds (alkaloids)
–Terpenoids(variety of essential oils)
–Phenolics(aromatic compounds including tannins and lignins)

3.Herbivore satiation: plants will undergo mast reproduction as not solely a response to abiotic factors –In mast years, oak (Quercusspp.) will produce more acorns than their predators can consume

4.Signalling: Some plants will emit chemical signal upon injury induced by herbivores attracting parasitic and predatory insects