Chapter 5 - Birth, Death, & Movement

Question 1

What is a population?

Answer 1

It describes a group of individuals of one species. It varies from species to species and from study to study.

Question 2

How does a population change?

Answer 2

It can grow or decline by changes in the number of individuals through birth or death (sometimes immigration/emigration)

Question 3

What is an individual?

Answer 3

It can be difficult to define individuals in certain cases because they can be unitary or modular.

Question 4

What is a unitary individual? What is another word to describe these types of individuals?

Answer 4

Unitary organisms are easily distinguishable and predictable (aka determinate because, for example, a spider has eight legs and it will never grow more legs, making it predictable).

ex. birds, insects, mammals, reptiles are all unitary

Question 5

What is a modular individual? What is another word to describe these types of individuals?

Answer 5

Modular organisms grow by repeated productions of modules, making them indeterminate/unpredictable (can’t easily know what total number is). Essentially modular is the repetition of basic structure that are attached and more can be produced.

ex. trees, shrubs, herbs, chain-forming bacteria,/algae, corals, sponges, etc are all modular because they continue to produce modules (like leaves, cells, etc.)

Question 6

What is a genet? Explain it in context of modular organisms.

Answer 6

It is a genetic individual. In modular organisms, the genet starts life as a single-celled zygote and will only be considered dead when all component modules that have been produced since have died.

ex. trembling aspens are all connected underground (clones), so together, they are a genet, but each single tree that appears to be individual (but isn’t) is a ramet (or module).

Question 7

Describe how an individual module works.

Answer 7

An individual module starts life as a multi-cellular outgrowth from another module and proceeds through its own lifecycle to maturity and death. As this is only one part of the genet, it’s overall development is still indeterminate.

Question 8

What is the mark-recapture method?

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Answer 8

It is a way of estimating a pop size by capturing a sample of individuals and marking them (through paint, leg ring, etc.), so that when another sample is captured, it gives an estimate of the whole population.

ex. 100 sparrow captures & marked; later, another 100 are captured and 50 are marked, so it suggests that the population is 200.

Question 9

What is an annual?

Answer 9

It is a plant organism that has just one generation each year.

Question 10

What is a perennial?

Answer 10

It is a plant organism that has a life cycle extended over several or many years. (For all organisms, a period of growth must occur before any reproduction)

Question 11

What is a biennial?

Answer 11

It is a plant organism that spends its first year in growth and usually dies in its second year, but sometimes later

Question 12

What is an iteroparous species?

Answer 12

They are species that breed repeatedly (more than once), devoting some resources during a breeding episode to further breeding episodes (if they live that long).

ex. occurs among most animals as well as annuals & perennials

Question 13

What are semelparous species?

Answer 13

They have a single breeding episode in their lifetime.

ex. biennials and salmon

Question 14

What is a seed bank?

Answer 14

It is a large population of dormant seeds buried in soil for further reproduction

Question 15

What is a cohort in a population?

Answer 15

It is all the individuals born in a particular period within a population. (follows specific group/cohort)

Question 16

What is a cohort life table?

DO Q7 pg.153

Answer 16

It records the survivorship of members in a specific cohort over time. In table:

• lx is the survival rate & gives survivorship curve
• mx is the reproduction of survivors
• lxmx is the number of individuals produced per age class
• if lxmx for each year is added up, R-knot (basic reproductive rate)

Question 17

What is a static life table?

Answer 17

It describes numbers of survivors of different ages when it’s not possible to follow cohorts. It provides a snapshot of a group/cohort.

Question 18

What is an age-specific fecundity schedule?

Answer 18

it tracks how much individuals of diff ages contribute to births in a pop as a whole

Question 19

What is the basic reproductive rate (R-knot)?

Answer 19

It is the sum of all the lxmx values and measures the overall extent that a pop has increased or decreased in a generation (aka in a cohort life table)

Question 20

What is a survivorship curve?

Answer 20

It plots log(lx) values against cohort age and it best shows constant survivorship

Question 21

Where does data in a static life table come from?

Answer 21

It comes from the age structure of a pop that was captured at one time & thus, should be used with caution.

Question 22

What are the 3 types of survivorship curves?

Answer 22

Type 1: mortality concentrated towards end of max lifespan
(ex. most typical of humans in developed countries and zoo animals)

Type 2: straight line signifying a constant mortality rate from birth to max age
(ex. typical of survival of seeds in a seed bank)

Type 3: extensive early mortality, but high rate of subsequent survival
(ex. typical of species that produce many offspring, most plants and animals, because few initially survive, but once the individual reaches a critical size, the risk of death remains low.

Question 23

What is an aggregated dispersal pattern?

Answer 23

It puts the pop in clumps

Question 24

What is a random dispersal pattern?

Answer 24

Its spread is random

Question 25

What is a regular dispersal pattern?

Answer 25

Its spread is evenly spaced. (movement and spatial distribution is intimately related)

Question 26

What is dispersal?

Answer 26

It describes the way individuals spread away from each other over time.

Ex. when seeds are carried away from a parent plant by wind or by an animal

Question 27

What is migration?

Answer 27

It refers to the mass directional movement of large numbers of a species from one location to another. Migration can be very different for different species.

Ex. from the movement of locust swarms to the small movement of intertidal organisms

Question 28

What is average density?

Answer 28

It is the total number of individuals divided by the total size of a habitat. (AvgDens=Ind/Hab)

Question 29

When do the highest dispersal rates occur?

Answer 29

They occur in crowded patches (emigration) to reduce competition for space and resources

Question 30

Why would dispersal occur at low densities?

Answer 30

Most often is to avoid inbreeding

Question 31

What is the carrying capacity (K)?

Answer 31

It is the density at the point where birth & death rates are equal (crossover point). It is an equilibrium.

Question 32

If densities are lower than K, what does this mean?

Answer 32

It means that births exceed deaths, so the pop will increase

Question 33

If densities are higher than K, what does this mean?

Answer 33

It means that deaths exceed births, so the pop will decrease.

Question 34

What is exponential growth?

Answer 34

It is when pops at low densities grow by simple multiplication over successive intervals of time

Question 35

Following exponential growth, what is a population’s rate of increase known as?

Answer 35

The intrinsic rate of natural increase, known as r.

Question 36

Why is exponential growth not practical? What type of growth pattern is often seen instead?

Answer 36

If pops continue to grow exponentially, they will run out of resources, so a logistic growth pattern is often seen.

Question 37

What is a logistic growth curve?

Answer 37

It occurs when there is a steady reduction in the rate of increase as densities move towards their carrying capacity. This gives rise to an S-shaped pop growth, known as logistic growth, that levels out at K

Question 38

What is net recruitment?

Answer 38

It is the number of births minus the number of deaths in a pop over a period of time (B-D). (Can be B-D+I-E).

If density is low, the net recruitment will be low because there are few individuals available to give birth or to die or too many at high densities. Therefore, the peak net recruitment is in the middle

Question 39

What is a trade-off?

Answer 39

It occurs because there are limited energy/resources available for growth/reproduction, so one function must be chosen (known as a trade-off): to grow more or to reproduce more

Question 40

What is the cost of reproduction?

Answer 40

It is when reproduction starts/increases, growth may slow or stop as resources are diverted towards reproducing

Question 41

What is an r species?

Answer 41

Their lifecycles are favoured by natural selection and they spend most of their life in a near-exponential, r-dominated phase of pop growth (b/c in an r-selected habitat)

Question 42

What is an r-selected habitat?

Answer 42

It is a habitat that has lots of resources (b/c its new), so there’s few other pops using them, resulting in a relatively easy life for the r species there.

Question 43

What are opportunistic species?

Answer 43

They are another name for r-species because they take advantage of opportunities presented by newly created environments

Question 44

What is a K species?

Answer 44

They spend most of their lives in a K-dominated phase of pop growth, close to the limits of resources and habitats (called K-selecting). This results in intense competition for the limited resources available, resulting in a more difficult life.