Midterm 1

Question 1

What is ecology?

Answer 1

The study of how organisms interact with each other and with the environment in which they live.

Question 2

What is evolution?

Answer 2

The study of how heritable traits change in populations over
successive generations

Question 3

Valuing biodiversity

Answer 3

•Market value
-US pharmaceutical research and development investments: >$50 billion annually

•Ecosystem services
•Tourism/recreation
•Cultural and intrinsic value
•Science/research
•Enjoyment

Question 4

Weather

Answer 4

current, short-term atmospheric conditions (e.g. temperature, rain, wind)
• “What should I wear today?”
•A big winter storm.

Question 5

Climate

Answer 5

average atmospheric conditions/patterns/cycles over many years/millennia
• “What clothes do I need to own for winter in Davis, California?”
•Typical patterns of flooding in a region

Question 6

latitude

Answer 6

•Latitude is described in degrees north or south of the equator

•Each degree north or south corresponds to ~69 miles of distance

Question 7

latitude

Answer 7

•towards th poles, more of the sun’s ray are absorbed because they must travel a longer distance through the atmosphere (north pole)

•At and near the equator, sunlight strikes Earth at a steep angel, delivering more heat and light per unit of area

•Towards the poles, the Sun’s rays strikes Earth at an oblique angel and are spread over a larger area, so that their energy is diffused (south pole)

Question 8

Hadley Cells

Answer 8

Hadley Cells are these patterns of atmospheric
circulation, with air rising near the equator (and raining), then descending as dry air at 30°N and 30°S

Question 9

Clouds

Answer 9

= moisture (rain)

Question 10

Dates are the same everywhere, but seasons are different in Northern and Southern Hemisphere

Answer 10

Equinox- March 20
Solstice- June 21
Equinox- September 22
Solstice- December 21

Question 11

Intertropical Convergence Zone (ITCZ) ≈ Thermal Equator

Answer 11

• The band of clouds/moisture/rain that shifts up and down periodically through the seasons
• The area with highest solar intensity

Question 12

Solar energy, Hadley cells, and climate

Answer 12

• Hadley cells: humid air rises (and forms clouds) near equator, drops as dry air about 30 degrees North and South.

• Average trend of humid tropical rainforest at equator, dry regions at 30°N and 30°S

• Because Earth’s axis is tilted, location of ITCZ/thermal equator moves (northernmost in June/July, southernmost in December/January).

• The E-W band around the Earth with the most rainfall (and clouds) shifts North or South at different times of year

Question 13

Rain Shadow

Answer 13

•Winds pick up moisture over the ocean

•on the windward side, air rises, cools, and releases moisture ae rain or snow, creating a wet climate

•On leeward side, dry air descends and warms, resulting in little rain and arid conditions

Question 14

atmosphere

Answer 14

-the air around the Earth

Question 15

greenhouse effect

Answer 15

Radiation from surface radiated back down to Earth

•Earth’s surface is warmed by incoming solar radiation and by back radiation from greenhouse gasses. this additional warming increases the outward radition from the surface.

•Greenhouse gasses in the atm absorb much of the surface reradition and radiate it back to the surface

Question 16

Greenhouse gas concentrations

Answer 16

-CO2

-N2O

CH4

CFC-12

CFC-11

HCF-22
HFC-134a

Question 17

CFC

Answer 17

any of a class of compounds of carbon, hydrogen, chlorine, and fluorine, typically gases used in refrigerants and aerosol propellants. They are harmful to the ozone layer in the earth’s atmosphere owing to the release of chlorine atoms on exposure to ultraviolet radiation.

Question 18

CFCs, ozone, and the chain reaction

Answer 18

• ozone is depleted to O2

-Effect of Montreal protocol

Question 19

CO2 is measured

Answer 19

This CO2 is measured directly by using ice cores – we can literally find ancient air and measure CO2 concentration.

Question 20

California Golbal heat record

Answer 20

• California is also generally warming – particularly in Southern California

• Relatively less snow is accumulating in the Sierra Nevada
mountains each Winter

•Of the 20 largest fires in California’s history (since
1932), 18 have occurred since 2000

Question 21

cryosphere

Answer 21

frozen water on Earth’s surface

Question 22

Decrease in global sea ice

Answer 22

•Sea ice has a typical annual pattern of increase and decrease.

•But the extent of sea ice has been declining over decades.

Question 23

Glaciers (+ ice sheets)

Answer 23

Glaciers- land based

Ice sheets- is the term for a large glacier (>50,000 km2)

Question 24

sea ice (+ ice shelves)

Answer 24

Iceberg- open ocean

Ice shelf- part of the Ocean

Question 25

Cryosphere to Hydrosphere

Answer 25

Melting of ice sheets and other glaciers

Question 26

hydrosphere

Answer 26

-liquid water on Earth’s surface

-sea levels are rising, the melting of the ice sheets and other glaciers

-Ocean absorbs heat, taking up any extra energy

-ocean warming up but slowly, causing tropical storms

-Ocean absorbs CO2 and acidities:
CO2 interacts with water (H2O) to create carbonic acid and free hydrogen ions.
Free hydrogen ions bind to carbonate to make hard-to-use
bicarbonate (rather than the carbonate that many organisms
need)

-As the ocean becomes more acidic effets marine life like corals, since they use CO2 to reinforce their shells

Question 27

Representative Concentration Pathways (RCP)

Answer 27

trajectories for greenhouse gas concentrations
• 4 possible climate futures
• Time at which the global greenhouse gas emission
peaks and starts dropping

• RCP 2.6: global annual GHG emissions peak 2010-
2020, then decline significantly
• RCP 4.5: global annual GHG emissions peak 2040
• RCP 6.0: global annual GHG emissions peak 2080
• RCP 8.5: global annual GHG emissions continue at
current level

The number (2.6, 4.5, ….) refers to the strength of greenhouse effect (called “radiative forcing”) predicted in year 2100
Bigger number means more greenhouse effect (because of more greenhouse gases)

Question 28

Levels of biological diversity

Answer 28

Genetic diversity: different in genotypes of individuals of the same species

Species diversity: different species occupying same habitat at same time

Other levels: different species assemblages in different habitats/ecosystems, species sharing evolutionary history, diversity in organisms’ ecological roles

Question 29

Biodiversity

Answer 29

-Not ever where

-most in the tropical

Question 30

Valuing biodiversity

Answer 30

• Market value: make money of plants

•Ecosystem services: bee pollinating

• tourism/recreation: open money to go into parks

• cultural and intrinsic value: a part of us

•science research: discover, know things

• enjoyment: positive impacts on people mental health

Question 31

Quantifying biodiversity

Answer 31

Diversity Index- D

Species richness= total # species in habitat

Species evenness= relative abundance of each species

𝐷 = (𝑝1^−𝑝1)(𝑝2^−𝑝2) (𝑝3^−𝑝3)…(𝑝𝑛^−𝑝𝑛)
p is the proportion of individuals of that species

Question 32

If the proportions were the same, but there were 200 frogs, how would D change?

Answer 32

Nothing would change, it’s all about propotion

Question 33

Quantifying biodiversity count

Answer 33

In most cases, you cannot directly count every organism

Instead, you may use quadrats or point counts, and then
extrapolate from this sample to the whole group

Question 34

Rarefaction curves

Answer 34

Instead of diversity as a function of area, we can look at
diversity as a function of the # individuals sampled

plots of the number of individuals on the x-axis against the number of species on the y-axis.

Question 35

Diversity curves and D

Answer 35

A higher D value = steeper curve

Question 36

Vicariance

Answer 36

The geographic separation of a species into separate populations through some sort of physical barrier

• continents were one Pangea)

• plate tectonics: broke Pangea into continents

• land bridge

• people building roads

Question 37

Most living tissues

Answer 37

•70% water by weight

•Ions and small molecules

• macromolecules

Question 38

Every living organism contains about these some proportions by weight of the four kinds of macromolecules

Answer 38

• Proteins: are chains of amino acids
- 20 amino acids
-building blocks of: Carbon, Nitrogen, Hydrogen, Oxygen

• nucleic acids: DNA and RNA
-Nucleic acids include RNA (ribonucleic acid) as well as DNA (deoxyribonucleic acid). Both types of nucleic acids contain
the elements carbon, hydrogen, oxygen, nitrogen, and phosphorus.

• carbohydrates (polysacchorides): Glucose is C6 H12 O6
- starch and glycogen

• Lipids

Question 39

Earth’s atmosphere

Answer 39

The atmosphere contains gaseous forms of carbon and nitrogen, but these are not easy to convert to more useable forms.

Question 40

Carbon and nitrogen

Answer 40

Carbon and nitrogen have to be “fixed” to become useful to most organisms. This kind of fixation was limited to
prokaryotes (bacteria and archaeons).

Question 41

Carbon fixation

Answer 41

Carbon fixation is storing the atmospheric carbon as a
carbohydrate, typically as glucose

Only bacteria could do this originally, but green plants gained
this ability through a symbiosis with a cyanobacterium. A
cyanobacterial symbiont became the chloroplast organelle

Question 42

Nitrogen-fixation

Answer 42

Nitrogen-fixation also occurs in bacteria and some archaeons. Gaseous nitrogen is comprised of two molecules of nitrogen with a triple bond between them. This triple bond is very hard to break and requires the enzyme nitrogenase

The product of nitrogen fixation is ammonia. In this form, nitrogen is available to many other organisms

Question 43

Photosynthesis

Answer 43

Photosynthesis occurs when atmospheric carbon (CO2) is
”fixed.” Fixation is storing the carbon as a carbohydrate, typically glucose

Question 44

Photosynthesis requires

Answer 44

•A carbon source

•An electron donor

•Light energy (photons) and a pigment to harvest the energy

•Bacteria use bacteriochlorophyll, plants have other pigments.

Question 45

WHEN water is used as the electron donor:

Answer 45

6CO2 + 12H2O + photons → C6 H12O 6 + 6O2 + 6H2O
carbon dioxide + water + light energy → carbohydrate + oxygen + water

Oxygen is released into the atmosphere.
This is oxygenic photosynthesis where carbon is fixed.

Photosynthesis that’s not oxygenic, but also Photosynthesis when oxygen is released

Question 46

Autotrophs

Answer 46

•Autotrophs live exclusively on inorganic sources of carbon, nitrogen, and other essential resources.
• There are chemoautotrophs and photoautotrophs. photoautotrophs which use sunlight as an energy source for metabolism and growth.
6CO2 + 12H2O + photons → C6 H12O 6 + 6O2 + 6H2O
carbon dioxide + water + light energy → carbohydrate + oxygen + water

Question 47

How is the light energy for photosynthesis harvested?

Answer 47

Plants have 2 major body divisions: the root and the
shoot.

Light is harvested in the shoot using pigments.

Question 48

Shoot system

Answer 48

The shoot system consists of stems and leaves, in which photosynthesis takes place

Question 49

Root system

Answer 49

The root system anchors the plant and provides water and nutrients for the shoot system

Question 50

Light exists in different wavelengths within the electromagnetic spectrum

Answer 50

Pigments absorb different wavelengths

• shorter wavelengths are more energetic

• longer wavelength are less energetic

• high wavelength = lots of light absorbed

• each wavelength have peak absorption, have two peaks

•

Question 51

Light can be absorbed or reflected.

Answer 51

The color of a plant is what it’s reflecting

Question 52

What kinds of pigments exist?

Answer 52

• Chlorophyll a: All plants (absorbs at 350-430, 600-700nm)
• Chlorophyll b: land plants + green algae, (420-470, 580-630nm)
• Chlorophyll c: dinoflagellates, diatoms, brown algae (400-440, 590-610 -minor)
• Xanthophyll (fucoxanthin): diatoms, brown algae (400-500nm)
• Phycocyanin: cyanobacteria (500-650nm)
• Phycoerythrin: red algae (450-550nm)

What every it’s mim is, is what its reflects

Question 53

Trade-off

Answer 53

the relationship between the benefits of a trait in one
context and its costs in another context

Ex: Why might Anacharis have 3 pigments?
- making 3 pigments allows the absorption of more pigments. However reflecting these 3 payments spend more energy making these

Ex: Why might two organisms living in the same place have different pigments?
- so you are not in competition with each other one could live in light and other in shadow.

Question 54

Principle of allocation

Answer 54

all life functions cannot be simultaneously maximized

Question 55

Autotrophs

Answer 55

Autotrophs live exclusively on inorganic sources of carbon, nitrogen, and other essential resources.

• shoots collects photosynthesis

• CO2 entire and O2 and H2O exit the leaves through pores on the leaf surface called stomata

Question 56

Stomata

Answer 56

the downside of opening stomata, plants could dry out

• under leaf to not dry out in the sun
• H2O enter through the roots

Question 57

There is variation in exactly how and where photosynthesis takes place.

Answer 57

In 85% of the plants, the carbon from CO2 is accepted by a 5-carbon structure called RuBP.

CO2 is fixed when the enzyme rubisco adds one carbon to RuBP to make a 6-carbon compound.
- mesophyll cells have rubisco and fix CO2 to RuBR to form 3PG

• C3 plant

•C4 plant

•CAM plant

Question 58

C3 plants

Answer 58

This 6-carbon compound quickly breaks into two 3-carbon compounds (3PG, so they are called C3 plants) that result in glucose production via the Calvin cycle.

All this takes place in the mid-leaf cells called
mesophylls.

Question 59

C3 plants stomata

Answer 59

Stomata: the more open they are, the more CO2 can enter, but the more water is lost (a trade-off). Most stomata open and close via guard cells, but this takes energy.

The enzyme rubisco binds CO2, but it also binds oxygen, so stomata stay open a long time to collect C02

Binding oxygen results in production of a 2-carbon
compound that has to be modified to enter the Calvin Cycle—the cost of modification reduces net carbon fixed by 25%. This is photorespiration. Fixed only get 75%

Question 60

C4 Plant

Answer 60

In about 8000 plants, mesophyll cells have a new enzyme, PEP, that binds CO2; PEP has a low affinity for oxygen, so stomata don’t need to stay open as long and it works if stomata are partially closed.

PEP carboxylase catalyzes formation of a 4-carbon storage compound. The 4-C compound diffuses into the bundle sheath cells. There CO2 is released!!

The extra CO2 prevents oxygen binding. Rubisco catalyzes the fixation of CO2 to 5-C RuBP so there is a 6-C compound that quickly makes two 3-C compounds for glucose production. This all takes place in the sheath cells.

More ATP is spent in the process. Better at high temperature, low CO2, and in drought conditions.

Initial CO2 fixation is spatially separated from the carbon fixation that leads to glucose production

Question 61

CAM plants

Answer 61

It is cooler at night, so stomata open then.
Photosynthesis requires light, so why do this—what is the trade-off?

-CO2 is fixed at night in mesophyll cells as a 4-carbon storage compound. It stored overnight in the cell vacuole.

-In the day, the 4-C compound moves to chloroplasts in the mesophyll cells. There CO2 is released!!

Rubisco catalyzes the fixation of CO2 to 5-C RuBP. The resulting 6-C compound quickly makes two 3-C compounds for glucose production.

The stomata are closed all day.

Initial CO2 fixation is temporally separated from the carbon fixation that leads to glucose production.

Question 62

living organisms the major elements of all these are

Answer 62

carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Question 63

Carbon and nitrogen

Answer 63

Carbon and nitrogen are present in gaseous forms, but they require special enzymes to ”fix” them into biologically useful forms.

Bacteria and forms derived from bacteria, such as a chloroplasts in plants, do this.

Question 64

plants need macronutrients

Answer 64

In addition to carbon, plants need macronutrients (e.g., nitrogen (N), phosphorus (P), potassium (K) and micronutrients (e.g., iron (Fe), Calcium (Ca), etc).

If a plant is short of a micronutrient, then the shoot grows poorly.

Where do plants get micronutrients and water? Roots

Nitrates and nitrites and phosphates are usually negative ions that are water soluble; plants absorb them with water.

K and Ca are positively charged ions where uptake is active.

Question 65

Another way to increase nutrient collection by roots

Answer 65

1) Plants form symbiotic relationships with root-loving fungi called
ecto-mycorrhizae. The fungi increase the root foraging area and may even connect plants with their neighbors

2) The roots of leguminous plants form symbiotic relationships
with a bacteria called Rhizobium that fixes nitrogen as ammonia. Nitrogenase does not work in the presence of oxygen, so plants invest energy in binding the oxygen to protect the bacteria.

Question 66

ecto-mycorrhizae trade off

Answer 66

Plant make CO2 to give sugar to the fungus

Question 67

Rhizobium cost

Answer 67

Leguminous plants: protect bacteria

Question 68

Organisms acquire nutrients through autotrophy or heterotrophy.

Answer 68

• Autotrophs live exclusively on inorganic sources of carbon, nitrogen, and other essential resources. There are chemoautotrophs and photoautotrophs.

• Heterotrophs use pre-formed organic molecules (those made by other organisms) to acquire carbon, nitrogen, energy, and other essential resources. They eat other organisms of all types.

• “Functional groups” of organisms share a mode of living such as heterotrophy, or carnivory

Question 69

Heterotrophs

Answer 69

Heterotrophs can be herbivores, carnivores, omnivores or detritivores

Herbivores spend a lot of time feeding and may need a diverse diet to meet all nutritional needs.

Carnivores feed much less frequently

Question 70

Heterotrophs: generalists & specialists

Answer 70

Heterotrophs may be generalists eating many different foods, like this locust,
Pro: more food choices

or specialists like this tobacco hornworm that feeds only on tobacco and its relatives.
Pro: not a lot of competition
Cost: detoxifying the poison

Question 71

stresses

Answer 71

Stress on organisms can be abiotic e.g., heating, cooling, drying, excessive wetness, salt concentrations, acidity, etc.
We will look at temperature stress.

Stress on organisms can biotic: e.g., consumers, competitors, etc.
We will look at stress as a result of consumers (predators/herbivores)

Question 72

abiotic stress:
Why does temperature matter?

Answer 72

Changes in temperature affect:
(1) the rates of biological reactions.
(2) the shapes of proteins, including the shapes of enzymes, so some processes may not work at extreme temperatures.
(3) the properties of biological membranes required for cell integrity

Question 73

abiotic stress: temp matter?

Organisms cope at the cellular level:

Answer 73

Organisms cope at the cellular level:
1. Organisms can make heat shock proteins (hsp’s), also called chaperonins, to stabilize the structures of other proteins and prevent inappropriate binding.
Cost a lot to do this

Hsp’s are present in almost all life from bacteria to humans.

2. Organisms can produce several versions of enzymes, each suited to different temperatures.

Question 74

Organisms have different thermal optima:

Answer 74

(1) some archaeons live in volcanic sulfur springs at 163 degrees Fahrenheit.

(2) Organisms have zones where they can regulate temperature, with and without spending energy.

•Within the thermoneutral zone, body temp is regulated by low energetic cost mechanisms, such as changes in blood flow to the skin and changes in posture

•Below the lower critical temp, the animal expends energy to produce metabolism heat

•Above the upper critical temp, the animal expends energy to lose heat by panting or sweating

Question 75

Ectotherms

Answer 75

Ectotherms: body temperature determined primarily by external conditions.
•Outside temp
• behavior allows it to regulate temp ie. Hind underground for more heat. Uses less energy

• exposing darkly pigmented back to the sun increases heat gain by radiation

• pressing flat against tree reduces heat loss by conduction

•ectotherms rely on morphological and behavioral mechanisms of temp regulation

Question 76

Endotherms

Answer 76

Endotherms: body temperature determined primarily by internal, metabolic rates.
• cost more in cold weather
• easy to stay at thermoneutral zone
•Endothermy is a high-benefit/high-cost strategy that works when resources (fuel for producing heat) are predictably abundant.

•Conduction is the direct transfer of heat when objects of different temp come into contact

•Warmer objects lose heat to cooler objects by radiation

•Evaporation of water from body surfaces or breathing passages cools he body

Question 77

What can organisms do with shape?

Answer 77

Leaf morphology:
•Reflective leaves reduce radiation gain. Dark leaves increase radiation gain

Plant morphology:

•Arctic and high altitude
-Low growth form reduces loss to conduction
-Hugs ground to gain conduction from rock
-Leaves perpendicular to the sun’s rays to increase radiation gain

•Desert
-Open growth form results in high loss to conduction
-Open form has less conductive gain
- Leaves parallel to the sun’s rays to reduce radiation gain

Question 78

What can animals do?

Answer 78

Endothermic:
•In rabbits, blood flow to ears with a large surface area allows heat exchange with the environment.
•Body shape conserves or releases heat—compare bunnies.

Ectotherms:
•Even ectotherms regulate blood flow to the skin; here iguanas increase heart rate to bring more blood to the skin to warm up.
•Behavioral regulation also occurs—e.g., spray water on yourself

Question 79

Evaporative heat loss occurs through panting, sweating, or transpiration (cools leaves).

Answer 79

High heat of vaporization:
• sweating uses evaporation of water to cool the body

Cohesion:
•waters cohesive strength helps it flow from the roots to the leaves in a tree
• as water is lose through stomata, root constantly bring water up through the plant

Question 80

For plants, water loss reduces photosynthetic rates.

Answer 80

• Plants can vary the number of stomata present by shedding leaves or making new leaves with fewer stomata.

• Some plants that live in extremely dry habitats (xeric habitats) have
stomata in internal pockets (crypts); hairs called trichomes reduce air flow to the pocket.

Question 81

Can it be too cold?

Answer 81

Ice crystals inside cells destroy cell organelles and membranes.

In response:
• Intracellular water is moved to the extracellular space.
• Urea and glucose are added to cells to act as a natural antifreeze.

These frogs freeze solid and still survive; most organisms cannot do that.

There are some thermogenic plants like the eastern skunk cabbage

Question 82

Stress due to the likelihood of being eaten is a biotic factor: Probability (p) of being eaten = p (detection) x p(capture) x p(consumption)
•detection

Answer 82

Probability (p) of being eaten = p (detection).
Reducing any of these factors increases survivorship (benefit), but adaptations are costly.

Costs:
(1) Need to stay in that habitat
(2) Reduced feeding time

Avoiding detection: camouflage or hiding

Question 83

biotic factor:
p(capture)

Answer 83

Probability (p) of being eaten = p(capture)
Reducing any of these factors increases survivorship, but adaptations are costly.

Avoiding capture: schooling, herding, masting.

Costs are increased numbers of competitors

Question 84

biotic factor:
consumption

Answer 84

Avoiding consumption:
(1) physical defenses
-Costs are in making the defense.

Question 85

Defenses may be constitutive (always present) or induced:

Induced

Answer 85

Induced animal defense example in the small aquatic arthropod ‘ Daphnia.

The invertebrate predators Chaoborus and Notonecta induced longer helmets, while the fish Lepomis induced shorter bodies but
had no effect on helmet length.

Longer tail spines (relative to body length) were induced by Notonecta and Lepomis.
The responses of D. retrocurva were influenced by algae concentration, with the more extreme responses occurring at a higher food concentration and higher lipid index.

Question 86

Adaptation vs. Acclimation

Answer 86

•Adaptation: evolutionary change in genotype that maximizes performance
Inuit people have lived above arctic circle for 10,000+ years
Barrel-shaped body, short limbs, subcutaneous fat all over body incl. hands, shunt blood to extremities

•Acclimation: change in phenotype within an individual’s lifetime to maximize performance (usually reversible)
World’s greatest long-distance, col water swimmer Body optimized at 40% body fat (internal wet suit)

Question 87

life history

Answer 87

The lifetime pattern of growth, reproduction, and survival for an
average individual.

Question 88

life history strategy

Answer 88

The way in which individuals within and among species allocate
resources to growth, reproduction, and survival based on genetic
and environmental factors

Question 89

Two very different patterns of investment in offspring:

Answer 89

• Few offspring, poor dispersal, lots of resources per offspring

• many offspring, broad dispersal, little investment per offspring

Question 90

Principle of allocation

Answer 90

Principle of allocation: Tradeoffs exist and there is no way that all
life functions can be maximized simultaneously; there must be
compromises between competing demands.

Each of these life history questions deals with resource allocation.

Any answer to one question has consequences for allocation to other events in the life history

Question 91

when to begin reproducing

Answer 91

•Reproduction diverts energy from growth.

•Size at first reproduction varies. Reproducing earlier generally means reproducing at a smaller body size. The sooner offspring are
made, the sooner they can make offspring, so there can be a advantage to reproducing early (compound interest argument).

•If delaying reproduction means you will make more offspring once you start reproducing, then delays can be advantageous, but there needs to be a high likelihood of living that long.
- however, you may die before this

Question 92

reproducing size

Answer 92

•In some cases, male animals begin to reproduce early and remain
much smaller than females.
- the available of sperm is early so they reproduce early meaning less energy to grow

•Reproductive males are smaller than reproductive females in
spiders and Crepidula.
-competition to find a female to mate with

•Reproductive males are many times larger than females in
Northern elephant seals.
- high competition with other males. Protect females, have to fight

Question 93

How many times in your life should you reproduce?

Answer 93

•Semelparous means you only reproduce once;

•iteroparous means you reproduce several times.

Question 94

R-selected

Answer 94

Offspring: many small
- dispersed; limited parental care

Parental size: small body size

Life span: short life

Allocation pattern: Allocate to rapid growth

Reproductive timing: Early reproduction

Number of reproductive events: Semelparous (high effort)

Population Density: Environmental conditions keep the population at low density

Habitat: Unpredictable, variable, harsh or disturbed

Sources of mortality: Mortality is independent of other organisms and often catastrophi

Question 95

K-selected

Answer 95

Offspring: Fewer large
-Not dispersed; more parental care

Parental size: Large body size

Life span: Longer life -

Allocation pattern: Allocate to slower growth, persistence, and defense

Reproductive timing: Delayed reproduction

Number of reproductive events: Iteroparous

Population Density: Environmental conditions allow populations of reach high density

Habitat: Predictable and favorable for growth and survival

Sources of mortality: Mortality is often caused by interactions with other organisms

Question 96

Factors influencing population growth

Answer 96

Equations are just (technically precise) sentences.
The change in population depends on births, deaths, and migration
into and out of the environment
∆𝑁 = 𝐵 − 𝐷 + 𝐼 − 𝐸
• N = current population size ∆N = the change in population size
• B = number of births
• D = number of deaths
• I = number of immigrants
• E = number of emigrants

Question 97

Exponential growth

Answer 97

Let’s ignore migration, then…
∆𝑁 = 𝐵 − 𝐷
• Births come from a birth rate (b) times the population size N
• Deaths come from a death rate (d) times N
∆𝑁 = 𝑏𝑁 − 𝑑𝑁
= 𝑏 − 𝑑 𝑁
= 𝑟𝑁
• We call r the intrinsic growth rate of a population. It incorporates
birth and death

Sentence version: the change in population size equals the
intrinsic growth rate times the current population size

Question 98

Predicting population size: exponential growth

Answer 98

We can “solve” the previous equation to get a prediction for the ‘ ‘ population size at time t.
𝑁𝑡 = 𝑁0𝑒𝑟𝑡
Sentence version: The population at time t depends on the initial population size and grows/declines exponentially through time (r determines the exact rate)

Nt is population at time t (in whatever units), N0 is population at time 0

For a population with 500 individuals, with r = 0.25 (per year), what will the population be after 10 years?
500e^(0.2510) = 6091.2 ≈ 6091 individuals

Question 99

Mark-recapture

Answer 99

In reality, N is usually unknown, so it’s simpler to rewrite as
𝑁 =(𝑛1 ∗ 𝑛2)/𝑀
(n1/N) = (M/n2)

n1: marked initially
N: estimated population size
M: marked recaptures
n2: total in second sample

Question 100

Does exponential growth occur?

Answer 100

•Generally, we expect exponential growth when looking at small populations that are recovering or newly established at a location

• Some r-strategist species (like the variety of grasshoppers referred to as locusts) will have exponential growth combined with periods of rapid mortality

• decline: lost of habitat

• If a population is able to reach a large enough size, population growth will slow down and eventually stop

Question 101

Density-independent controls

Answer 101

•Factors affecting population size that DO NOT depend on the number of organisms in the population, usually abiotic factors

• drought: weather

•Factors affecting population size that DO depend on the number of organisms in the population, usually biotic factors
-Density-dependent controls prevent a population from growing forever
- disease
- predation
- limited resources (e.g. Space)

Question 102

Logistic growth: differential equation

Answer 102

(dN/dt) = rN [(K-N)/K]

Just one new term affectinggrowth rate (K-N)/K

Sentence version: the change in population size equals the intrinsic growth rate times the current population size times a factor that shrinks as the population size approaches K.

When N is large, (K-N)≈0, so (K-N)/K ≈0 Growth slows to 0

When N is small, (K-N)≈K, so (K-N)/K ≈1 Growth is nearly exponential

Question 103

Logistic growth: predicting population size

Answer 103

Nt= {K/1+[(K-N0)/N0]e^(-rt)]}

This term goes to 0 as t increases (so Nt goes to K). This happens faster when r is larger.

Question 104

R-strategist species

Answer 104

r-strategist species tend to have a high intrinsic growth rate (r), but
density-independentfactors prevent populations from reaching their carrying capacity

Question 105

K-strategist species

Answer 105

K-strategist species tend to have lower r and population size is often near carrying capacity K