APES Unit 3 Test

Specialists

any species that has a more narrow range of tolerance, or a narrower ecological niche that makes them more prone to extinction

Generalists

species that have larger range of tolerance, broader niche that makes them less prone to excitation and more likely to be invasive

What are characteristics of specialists?

• Narrow niche

• Less adaptable because of specialized needs

• More likely to become extinct

• Use a specific set of resources

• Easily affected by changing conditions 

• Have an advantage when conditions are more constant

What are characteristics of generalists?

• Broad niche 

• Adaptable to many environments 

• Less likely to become extinct 

• Use a variety of resources

• High range of tolerance

• Have an advantage when conditions change

Where are specialist species more advantaged?

in habitats that remain constant

Where are generalists more advantaged?

in habitats that are changing

What are two reproductive strategies?

K-selected and R-selected

What are K-Selected Species?

“quality”.

Species that have few offspring with heavy parental care to protect them. They may only reproduce once. They have a long lifespan and a slow population growth rate.

What is more likely to impact K-Selected species than R-Selected Species?

environmental change or invasive species

Characteristics of R-Selected Species

“quantity” 

they have many offspring, with little to no care. They reproduce many times. They have a shorter lifespan and a high population growth rate

Are K-Selected or R-Selected species more likely to be invasive?

R-Selected species

What are R-Selected species better suited for?

rapidly changing environmental conditions 

What does having a longer lifespan as a K-Selected species lead to?

it leads to them to take a long time to reach sexual maturity, which leads to low biotic potential and a low population growth rate

What does having a shorter lifespan as a R-Selected species lead to?

it leads them to reach sexual maturity quickly, which leads to high biotic potential and a high population growth rate

Characteristics of K-Selected Species

• Long life span 

• Long time to reproductive maturity 

• Few number of reproductive events 

• Few number of offspring 

• Large size of offspring 

• Present parental care

• Slow population growth rate 

• Density dependent population regulation independent 

• Stable, near carrying capacity

Characteristics of R-Selected Species

• Short life span 

• Short time to reproductive maturity 

• Large number of reproductive events 

• Large number of offspring 

• Small size of offspring 

• Absent parental care

• Fast population growth rate 

• Density population regulation independent 

• Highly variable

What does low biotic potential in K-Selected species lead to?

it’s hard for the population to recover after a disturbance (environmental change)

What can high parental care in K-Selected species lead to?

death of a parent meaning the death of the offspring

Are K-Selected or R-Selected species more likely to go extinct?

K-selected

What is the relationship between K-selected and R-selected species?

Invasive species (usually r-selected species) outcompete K-selected species for resources with high biotic potential and rapid population growth 

Are K-selected or R-selected species less likely to adapt?

K-selected

What does high biotic potential in R-selected species lead to?

more rapid population recovery after a disturbance

What does low parental care in R-selected species mean?

the death of parent doesn’t impact offspring

Why are R-selected species less impacted by invasive species?

because their population grows quickly and they are more likely to be invasive themselves

What does a larger population and faster generation time in R-selected species lead to?

a higher chance of adaptation and lower chance of extinction 

Biotic Potential

the maximum reproductive rate of a population in ideal conditions and no limiting resources

What are the reproductive strategies of a species a product of?

adaptation and natural selection

What is competition like in K-selected species’ habitats?

relatively high

What is competition like in R-selected species’ habitats?

relatively low

How do the concepts of K-selected and R-selected species apply in natural life?

Many species have reproductive strategies that are not uniquely one or the other, or they change in different conditions at different times 

Survivorship Curve

line that shows survival rate of a cohort (group of same-aged individuals) in a population from birth to death

What does a faster drop in line of a survivorship curve mean?

quicker die-off of individuals

What does a slower drop in line of a survivorship curve mean?

longer average lifespan

Why are there no x-axis labels on a survivorship curve graph?

because it’s relative to the different lifespans of species

Type I Curves

• mostly K-selected

• High survivorship in early and mid life, decreases in late life

• most mammals

Why do Type I species have high survivorship in early life?

high parental care

Why do Type I species have high survivorship in mid life?

large size and defensive behavior

Why do Type I species have a decrease in survivorship late in life?

old age sets in 

Type II Curves

• in between Type I and Type III

• Steadily decreasing survivorship throughout life 

Type III Curves

• mostly r-selected

• low survivorship at early life, declines steadily mid life, slow decline in late life

• Ex. insects, fish, plants

Why do Type III species have low survivorship in early life?

due to little to no parental care

Why do Type III species have a steady decline in survivorship in mid life?

because few make it there at all

Why do Type III species have a slow decline in survivorship in late life?

old age

Carrying Capacity

the maximum number of individuals in a population that an ecosystem can support (based on limiting resources)

How is carrying capacity represented on a graph?

population growth starts off an exponential, and levels out around a certain number

What are some limiting resources that impact carrying capacity?

• Food

• Water 

• Habitat (nesting sites, space)

Overshoot

when a population briefly exceeds carrying capacity

What is an example of overshoot?

Deer breed in fall, give birth all at once in spring. The sudden spike in population is overshoot

What happens when population overshoot occurs?

Because the individuals can’t be supported by environment, they will die, and later be replenished to carrying capacity

Consequences of Overshoot

resource depletion

Die-Off

Sharp decrease in population size when resource depletion (overshoot) leads to many individuals dying 

What is an example of die off?

Reindeer of St. Paul Island. 25 were introduced in 1910, growth was gradual (10’-30’), then exponential (30’-37’). Carrying capacity was overshot. Sharp die-off led to population crash as food resource (lichen) were severely depleted

How is the idea of carrying capacity somewhat ideal when it comes to natural life?

Real populations don’t always fluctuate around carrying capacity. If resource depletion is severe enough, total population crash can occur 

K

carrying capacity

R

biotic potential

What are four population characteristics?

size, density, distribution, sex ratio

Size (N)

total number of individuals in a given area at a given time

What is good about a larger population size?

safer from population decline

Density

number of individuals/area

What does high density in a population lead to?

higher competition, possibility for disease outbreak, possibility of depleting food source 

Distribution

how individuals in a population are spaced out compared to each other

What are the three kinds of distribution?

• random

• uniform 

• clumped

What is an example of a random distribution?

trees

What is an example of a clustered distribution?

herd/group mammals, humans

What is an example of a uniform distribution?

territorial animals

Sex Ratio

ratio of males to females. Closer to 50:50, the more ideal for breeding (usually)

How can a bottleneck event or die-off affect sex ratio?

skewed sex ratio (not enough females) limiting population growth

Density-Dependent Factors

factors that influence population growth based on size

What are examples of density-dependent factors?

food, competition for habitat, water, light, even disease

Why is it called density-dependent factors?

these factors limit population growth based on their size. Small populations don’t experience these, large do

What do density-dependent factors put on a population?

competitive pressure

What do density-dependent factors tend to be?

biotic, have a strong influence when the number of organisms per unit area reaches a certain level

What is an example of a density-dependent factor and a limiting resource? 

Food. When twice as much food was added to the dish, both species increased carrying capacity by about 2 times

Density-Independent Factors

factors that influence population growth independent of their size

What is an example of a density-independent factor?

natural disasters (flood, hurricane, tornado, fire)

What does being a density-independent factor mean?

It doesn’t matter how big or small a population is, it limits them both

What do density-independent factors tend to be?

abiotic, have an effect on all populations, regardless of size or density

Biotic potential may occur initially but…

limiting resources (competition, food, disease, predators) slow growth, and eventually limit population to carrying capacity

What type of graph is biotic potential?

Exponential growth

Logistic Growth 

initial rapid growth, then limiting factors limit population to K

What are inputs that increase population size?

immigration and births

What are inputs that decrease population size?

emigration and deaths

What is the equation for population size accounting for changes in population?

initial population + ((immigrations + births) - (emigrations+deaths))

What is population growth limited by?

environmental factors, especially by the available resources and space

When the resources needed by a population for growth are abundant, population growth usually…

accelerates

When the resource base of a population shrinks, the increased potential for unequal distribution of resources will ultimately result in…

increased mortality, decreased fecundity, or both, resulting in population growth declining to, or below, carrying capacity

Age Cohorts

groups of similarly aged individuals

Ages 0-14

prereproductive

Ages 15-44

reproductive age

Ages 45+

post reproductive

What does the size difference between 0-14 and 15-44 indicate?

growth rate

What does a larger 0-14 cohort indicate?

current and future growth

What does a roughly equal 0-4 and 15-44 cohort indicate?

slight growth/stable

What does a larger 15-44 cohort indicate?

population decline

What is an age structure diagram also called?

a population pyramid

What does an extreme pyramid shape of an age structure diagram mean?

rapid growth 

What does a less extreme pyramid shape of an age structure diagram mean?

slow, stable growth

What does a house shape of an age structure diagram mean?

stable, little to no growth

What does an upside down pyramid shape of an age structure diagram mean?

declining population