BIO 211: Unit 6

*There are several methods animals use to orient themselves as they migrate, including the north star, magnetic fields, and piloting. What is piloting?
Piloting is when the animal remembers specific landmarks that help orient its movements during migration.

*The pH of a solution is 7.4. What is the concentration of protons (H+) in the solution?
3.89 × 10−8 M

*The annual growth rate (r) of a population is 0.02. The initial population has 550 individuals. How many individuals would be in the population after 12 years?

*Examine the figure. Why was the island area plotted on a log scale?
So that graph of the number of species versus the log island size (km2) would be linear.

*In the figure below, Mb equals mammal body mass and fH is the heart rate. What is the average heart rate of a mammal with a mass of 400 g?
262 beats per minute

*Radioactive decay occurs exponentially. The equation A = Ao e(−0.693t/T1/2) where Ao is the initial amount of radioactivity, t is the time between the initial and final measurement, and T1/2 is the half-life. You purchased 10 microcuries (10 μCi) of radioactive phosphorus, 32P. The half-life of 32P is 14.29 days. You use the phosphorus 8 days later to label DNA. How many μCi of 32P did you use?
6.78 μCi

*Why might a decorated nest in bowerbirds be a reliable signal of male quality?
Individuals must invest high amounts of energy to produce such a nest.

*Why does altruism seem paradoxical?
Alleles that cause an organism to behave altruistically should be selected against since these alleles should lower the organism’s fitness.

*The Sun is difficult to use as a compass because its position changes during the day. How do birds that navigate by the Sun adjust for this change?
They use an internal clock that tells them the time of day.

*QUANTITATIVE Hamilton’s rule states that an altruistic allele could spread in a population if Br > C, where B represents the fitness benefit to the recipient, r is the coefficient of relatedness between altruist and recipient, and C represents the fitness cost to the altruist.

If r = 0.5 between the altruist and the recipient, what would the ratio of costs to benefits have to be for the altruistic allele to spread?

C/B< 0.5

*The study of the Laceta vivipara lizard showed that _____.
the low-elevation Netherlands population was intermediate for fecundity and survivorship when compared with other populations

*Why are biologists convinced that the sex hormone testosterone is required for normal sexual activity in male Anolis lizards?
Male Anolis lizards whose gonads had been removed did not court females.

*Which of the following statements about the waggle dance of the honeybee is not correct?

Sounds and scents produced by the dancer provide information about the nature of the food source.
The speed of waggling is proportional to the distance from the hive to a food source.
The length of a waggling run is proportional to the distance from the hive to a food source.
The orientation of the waggling run provides information about the direction of the food from the hive, relative to the Sun’s position.

The speed of waggling is proportional to the distance from the hive to a food source.

*What is the measure of relatedness (r) between first cousins?
1/2 × 1/2 × 1/2 = 1/8. For example, your father’s (1/2) brother’s (1/2) son (1/2).

*According to the competitive exclusion principle, two species cannot continue to occupy the same _____.

*Which concept(s) for identifying species CANNOT be applied to asexual or fossil species?
Biological species concept

*In what respect do hominins differ from all other anthropoids?
Bipedal posture

*Which lake zone does not receive sunlight?
The aphotic zone

*Fixed action patterns are examples of _____.
Innate behaviors.

U6 26

Behavioral ecology
– action or reaction of individuals in response to a stimulus (internal or external)
• feeding / hunting
• reproduction
• orientation
• predator avoidance
• communication

Proximate causation (mechanistic)
– how actions occur
– mechanisms within the individual that make the behavior possible

Ultimate causation (evolutionary)
– why actions occur
– evolutionary causes: why has the animal evolved those mechanisms in the first place

FAPs = fixed action patterns
– a sequence of behavioral acts that is unchangeable and usually carried out to completion once initiated

Nurture: learned behavior
– flexible behavior
– experience-based modification of behavior – cost-benefit analysis
ex: birds that get bugs from holes with sticks

– Associative learning: associating one stimulus with another
1. Classical conditioning associating arbitrary stimulus with reward or punishment
2. Operant conditioning trial & error learning

Foraging behavior
– can be inherited (e.g., fruit-fly larvae)
Rovers – offspring of rovers tend to be rovers
Sitters – offspring of sitters tend to be sitters
– optimal foraging
• maximize energy intake
• minimize cost of finding and ingesting food • weighing risk of being eaten

Question: Do gerbils “weigh” the costs and benefits of foraging?
Hypothesis: Gerbils reconcile the risk of predation and the benefits of extra food availability
Null hypothesis: Foraging activity is independent of predation and food availability.
34 gerbils
Treatment 1: No owl fly-overs, no extra seeds
Treatment 2: Owl fly overs, No extra seeds
Treatment 3: Owl flyovers, extra seeds
#1 more time in the field, #2 less time in the field, #3 about even

Sex hormones
Control mating behavior

Often complex, ritualized behavior

Nature: innate or instinctive behavior
– inflexible and stereotypical behavior patterns
– developmentally fixed, not based on experience – e.g., baby bird begging for food

Sexual activity
Can be affected by multiple stimuli

Habitat density and quality affect fitness

Why do animals migrate?
Increased food access
higher reproductive success but high cost

How do animals navigate?
Piloting – familiar landmarks
Compass orientation – specific direction True navigation – location of specific place
ex: Green sea turtles use magnetic map orientation to navigate

Signal received and acted on

Social process
Social process
e.g., honeybees food location
round dance (food within 80-100 m from hive) waggle dance (food over 100 m from hive)

Deceitful communication
– deceiving another species – deceiving own species
ex: Hognose snakes play dead to avoid being eaten. Female footers fireflies flash the courtship signal of another species and then eat males that respond.
idea of female “mimics”

Fitness cost associated with fitness benefit to recipient (self-sacrificing behavior)

Hamilton’s rule
Br > C
B – fitness benefit to beneficiary
r – coefficient of relatedness (0 – 1)
C – fitness cost to actor
altruistic behavior favored when B high, r high and C low

Kin selection
Altruistic behavior favored when
B high, r high and C low

Direct fitness
Derived from individual’s own

Indirect fitness
Derived from helping relatives produce more offspring

Inclusive fitness
Combination of direct and indirect fitness

– involuntary altruism
– colonies e.g., bees, wasps, ants
– workers sacrifice reproduction to rear queen’s offspring

Reciprocal altruism
– fitness exchange separated in time
– non-related individuals e.g., vervet monkeys, vampire bats

Group of individuals from same species that live in the same area at the same time

Populations connected by migration

Number of individuals

Geographic distribution

Number of individuals per unit area

Pattern of spacing individuals
(clumped, uniform, random)

Study of size and structure of populations through time
populations grow due to birth and immigration populations decline due to death and emigration

Life table
Life table
Probability for survival and reproduction (age class, survivorship, age specific fecundity)

Survivorship curves
Survivorship curves
Type I curve – high survivorship throughout life, most individuals reach maximum life span (humans)
Type II curve – relatively constant survivorship throughout life (songbirds, squirrels)
Type III curve – high death rates early in life, high survivorship after maturity (many plants)

Life History strategies
Fitness trade offs

Growth rate
– change in numbers of individuals (ΔN) per unit time (Δt) – without immigration or emigration: ΔN/Δt = r * N

Per capita rate of increase (r)
– difference between birthrate (b) and death rate (d) per
individual: r = b – d
b > d, r > 0 (population grows)
b < d, r < 0 (population declines)

Exponential growth
ΔN/Δt = r * N – r does not change over time
– density independent population

Carrying capacity (K)
– maximum number of individuals that can be supported
in a particular habitat
– can change depending on conditions (food, space, water, soil quality, resting/nesting sites)

Logistic growth equation
ΔN/Δt = r * N ((K – N) / K) – density dependent

Density dependence
• If N is far from K, acts like exponential growth
• If N is close to K, very little (to no growth)
• Generates logistic curve (s-shaped), approaching K

Limitations to growth rates
– density-independent factors
(weather patterns, environmental disasters)
– density-dependent factors
(predation, competition, parasites, diseases)

Population cycles
Regular population size fluctuations
Density-dependent factors

The Passenger Pigeon
The Passenger Pigeon, once were billions,
is extinct since 1914

Antarcic “krill” populations have decreased 40 – 80% since 1979
Deceased krill populations have led to over 50% decline in populations of Adélie and Chinstrap Penguins in the Antarctic Peninsula

Brown tree snakes
Brown tree snakes, unintentionally introduced to Guam have caused the extinction of 12 bird and 6 lizard species

What is demography?
Study of size and structure of populations through time
populations grow due to birth and immigration populations decline due to death and emigration

What are the three types of survivorship?
Type I curve – high survivorship throughout life, most individuals reach maximum life span (humans)
Type II curve – relatively constant survivorship throughout life (songbirds, squirrels)
Type III curve – high death rates early in life, high survivorship after maturity (many plants)

What are the differences between exponential growth and logistic growth?
Exponential growth does not change over time and has a density independent population
Logistic growth is density dependent

What are density dependent vs. independent mortality factors?
– density-independent factors
(weather patterns, environmental disasters)
– density-dependent factors
(predation, competition, parasites, diseases)

Interacting species within a certain area
• depend on historical features, landscape features, abiotic and biotic factors

One species fitness benefit, other species unaffected (+/0)
Can be conditional, e.g., antbirds
Ants stir up insects while hunting, the ant bird tags along and benefits

Both species use the same resources, lower fitness for both (-/-)
Intraspecific – between same species Interspecific – between different species

Competitive exclusion principle
Two species with exactly the same requirements cannot live together in the same place

Total sum of an organisms use of abiotic and biotic resources in its environment
Interspecific competition occurs when niches of two species overlap
natural selection acts on both sides to avoid competition (niche overlap)
– niche differentiation / resource partitioning (change in resources)
– character displacement (change in traits)

Fundamental niche
Total environmental space in which a species can exist

Realized niche
Realized niche
Actual environmental space in which a species does exist

One species benefits by eating or absorbing nutrients from another species, which fitness declines (+/-)

Plant consumption by herbivores

Tissue consumption of host by parasite

Prey consumption by predator

Constitutive defenses (always present)
– armor and weapons
– toxin or defense chemicals
– cryptic coloration
– escape behavior
– schooling / flocking

Close resemblance of other species

Müllerian mimicry
Müllerian mimicry
Harmful species resembles harmful species
Looks dangerous…is dangerous

Batesian mimicry
Batesian mimicry
Innocuous species resembles harmful species

Inducible defenses
– defense trait only produced in response to predator presence
– e.g., mussel shell thickness and attachment adhesion changes in presence of crabs

Two species interact with fitness benefits for both (+/+)
Involve variety of species and rewards
(eg: cleaner shrimp and fish)

Community structure
Stable in final stage (climax community)
Keystone species

Keystone species
More impact on community structure than its abundance and biomass would suggest

Keystone predator: Pisaster (starfish)
Intertidal communities in the Pacific northwest
When Pisaster experimentally removed, species diversity greatly reduced

Community development after disturbance (depends on type of disturbance, frequency and severity)

Primary succession
Primary succession
– no soil present, lifeless area
– e.g., glacial recession, surface of lava flow

Secondary succession
Secondary succession
– soil largely intact, existing community removed
– e.g., abandoned agricultural fields

Species interactions affect succession
Early arriving species creates favorable condition for later arriving species

Species interactions affect succession
Existing species have no effect on subsequent species

Species interactions affect succession
Presence of species inhibits establishment of another species

Species richness
Total number of species present in community

Species diversity
Incorporates species relative abundance

Richness and diversity depend on
Habitat size
Latitudinal gradient

Habitat size
Species richness and diversity
declines with decreasing habitat size

Species richness and diversity declines with increasing remoteness

Latitudinal gradient
Species richness and diversity declines with increasing latitude

– all species communities present in a region along with abiotic components such as soil climate, water, and the atmosphere
– biotic and abiotic components are linked by energy flow and nutrient cycling
Can be small (pool in a cave), can be large (global ecosystem)

Energy flow through the ecosystem
sun, geothermal energy

Primary producers (autotrophs)
– convert energy to chemical energy (compounds)
– chemical energy supports all other living organisms

Gross primary productivity (GPP)
Total amount of chemical energy produced

Net primary productivity (NPP)
(R – energy used for cellular respiration)

Trophic levels
– primary consumers (eat primary producers)
– secondary consumers (eat primary consumers)
– tertiary consumers (eat secondary consumers)
– decomposers (eat detritus)

Food chain
Food chain
Connects trophic levels in an ecosystem
Describes how energy flows

Food web
Food web
– more accurate description than food chain
– consumers often feed on multiple levels

Biomass eaten alive or dead – herbivores versus decomposers
Typical forest:
5-7% live leaves to primary consumer
93-95% dead leaves to decomposers
Typical marine system:
35-40% live algae to primary consumer
60-65% dead algae to decomposer

Productivity pyramid
Productivity pyramid
– energy availability declines with higher trophic levels
– only about 10% of biomass transferred between trophic levels
Agriculture could support a larger human population if we were all “vegetarians”

Certain molecules increase in concentration as they are transferred between trophic levels (e.g., heavy metals like mercury, organic pollutants such as herbicides or pesticides)

Top predators
Sometimes predators regulate entire ecosystems

Top-down control
A consumer limits a prey population

Trophic cascade
Trophic cascade
Changes in top-down control cause effects on multiple levels in a food web (e.g., keystone species)

Global productivity
NPP higher on land than in oceans (more light) Marine NPP highest along coastlines
Terrestrial NPP highest in wet tropics (temperature, water)

Terrestrial nutrient cycle
Terrestrial nutrient cycle

Global nitrogen cycle
Global nitrogen cycle
– nitrogen fixation (NH3) by humans
— increased productivity of terrestrial ecosystems
– pool of molecular nitrogen (N2) in atmosphere
– over-fer tilization leads to “dead zones” in aquatic ecosystems

Global carbon cycle
Global carbon cycle
– photosynthesis, respiration
– reservoirs (ocean, fossil fuels, biomass, atmosphere)

Greenhouse effect
Greenhouse effect

Human impacts on global carbon cycle
Burning of fossil fuels releases CO2 into the air
Only 64% of US adults think that climate change is happening…
Ice core data highest CO2 in ~650,000 years
Global temperatures increased ~0.8oC since 1860

Current and future impacts
– CO2 concentrations continue to rise
– average global temperature increases
– polar ice caps melt
– sea level rises
– change in precipitation pattern
– increased storm intensity

Are human activities causing global climate change?
– the available data support the conclusion that the answer is “yes”
– our best current data indicate that at least 74% of the warming in the past 50 years is due to human activity

– summarized in the tree of life
– measured in species richness and species diversity
– changes drastically depending on the region or biome

Biodiversity hotspot
A region with high number of endemic species A region of urgent conservation need

6th mass extinction
– increasing extinction rates
– faster extinction rates than ever before
– International Union for the Conservation of Nature (IUCN) red list of threatened species:
vulnerable, endangered, critically endangered
13% Birds threatened
25% Mammals threatened
41% Amphibians threatened

Habitat destruction and fragmentation
– deforestation
– grazing livestock
– filling in wetlands
– building housing

Unsustainable removal of species

Invasive / introduced species
Non-native species introduced in new area and disrupts native species
Biodiversity threats

Changes in both abiotic and biotic environments due to release of chemicals

Climate change
Loss of coral reefs due to “bleaching”
Loss of habitat in arctic and alpine tundras
Slow dispersing or sessile species unable to track climate changes
Ocean acidification due to carbon dioxide increase

Biological benefits
– more productive ecosystems due to higher resource use efficiency and facilitation
– increased community stability due to higher resistance and resilience

Economic and social benefits (ecosystem services)
– provisioning services (raw materials, food, medicine) – regulating services (soil, climate, erosion, water, air) – cultural services (recreation, health, living quality)
– supporting services (primary production, nutrient cycling, pollination)

Protect the biological diversity

To live off resources that are being produced continuously

Invasive species management
Plans to limit spread and prevent introduction

Ex situ conservation
Preservation of species in zoos, aquaria, ranches, and botanical gardens for potential reintroduction

Sees banks
Long-time storage to protect loss of genetic diversity

Wildlife corridors
Encourage gene flow and allow recolonization

Wildlife refuges
Protective areas

Genetic restoration
Creating artificial gene flow in endangered species

Ecosystem restoration
Restore or reforest heavily degraded or lost ecosystems

What can we do?
– be informed
– be mindful about your use of energy and resources
– reduce, re-use and recycle
– think globally and act locally

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