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T.A. BLAKELOCK GRADE 12 BIOLOGY
Population Dynamics
UNIT 5 POPULATION DYNAMICS
A. CHARACTERISTICS OF POPULATIONS
1. Terms
a. ______________ – a group of individuals of the same species living in the same geographical area
b. _________________ – the number of individuals of the same species
occupying a given area/volume at a given time
c. ___________________ – the number of individuals of the same species
that occur per unit area or volume
________________ = population number
space occupied
D = N.
S
d. crude density vs ecological density
___________________ = the population number divided by the total area
___________________ = the pop number divided by the usable area
eg. for fish density in a park,
we only want their density in the area of lakes or rivers, not the total area of the park
e. ____________________
the general pattern of individuals within an area
2. Calculating population characteristics
eg A. A population of 450 porucpines live in ana rea 12.1 km by 15.3 km in which there are three
lakes [7.1 km2, 15.2 km2 and 2.7 km2]. What is the crude density of this population?
What is the ecological density?
eg. B If the wolf population density in an area is 0.093 wolves /km2 and the study area is 47.3 km
by 60.4 km, how many wolves would there be in the area? How many wolves would be in the area
if there is a lake of 361.3 km2 in the area?
3. Mark – Recapture Method of Counting
a. some individuals in a population are____________, ___________ or ___________ in some way
b. the marked individuals are then _________________
c. the experimenters then wait a time, return and ________________ individuals in the same area
d. they note whether the captured animals are____________ [recaptured] or _____________ [new]
e. they determine the______________ population in the area with the formula
total# marked [
]
total population [____]
=
# of recaptures
[
]
size of second sample [____]
eg. In a population of unknown size – researchers capture and mark 72 mink. After release,
they capture 65 individuals on a second trapping, of which 8 are marked.
What is the total population of mink?
4. Quadrat sampling
a. a quadrat is a sampling frame used to estimate population ____________
b. the ____________ may be 1.0m x 1.0m for small species or 100m x 100m for large species
c. the quadrat only works for ____________ species [ones that don’t move] eg trees, barnacles
d. usually more than one quadrat is counted & then _____________ values are used
eg using a 10m by 10m quadrat, young pines trees were counted in an area with the following
results.....23, 17, 19, 25. What is the population of pine trees in an area 2.3 km by 1.7 km?
B. CHANGES IN POPULATION SIZE
1.
Population growth models
a. ______________ growth
for populations with ____________ breeding times
eg. one breeding cycle per year
b. _______________growth
for populations that are ____________ growing
c. _________________ growth rate
growth that levels off as the population grows towards its carrying capacity
_____________________ – the maximum number of organisms that can be sustained
by the available resources over a period of time
_____________ phase
pop
size
_____________phase
_______ phase
________ phase
time
__________ phase – slow growth at start as get established
__________ phase – rapid growth when population is settled in new area
__________ phase – long term pattern fluctuates, but always below carrying capacity
__________ phase – pass carrying capacity, damage environment and so pop is reduced
2.
affecting population change
___________,
3.
______________,
________________ & __________________
Types of populations
a. ____________ population – all 4 factors affect population
b. ___________ population – no emigration or immigration to change the population
4.
percentage population change
% population change
=
Complete Populations and carrying capacity
C. FACTORS AFFECTING POPULATION CHANGE
1. Density Dependent Factors – factors that have a greater effect when the pop density is ______________
a. __________________ competition
- individuals compete for nest space, food, light, etc, with others of the ___________ species
- eg. high density trees – lots of shade, little water, few nutrients per tree
b. _____________________
from a predator viewpoint
- more prey / predator -- predator has _________________
- less prey / predator -- predator has more __________________________
from a prey view point
- more prey / predator – prey has less chance of being _____________________
- less prey / predator – prey has more chance of being _____________________
Populations and Carrying Capacity [Gulls & Terns]
The common tern is a small, delicate bird that eats only fresh fish. The ring-billed gull is a larger, aggressive bird that
eats fresh fish, garbage and just about anything it can get its beak onto. Both species nest in colonies with their nests
little more than depressions in the soft sand portion of the land. Both species migrate south for the winter, with the
gulls arriving back in April and the terns arrving back in May.
Graph of population, in June, for common terns
and ring-billed gulls
on the Leslie Street Spit, Toronto.
1200
1100
1000
900
population numbers
800
700
600
500
400
300
200
100
1976
1980
1984
1988
1992
19 96
2000
years
1.
Determine the carrying capacity of this environment for the common terns, explaining your work
a. prior to the arrival of the ring-billed gulls?
b. after the ring-billed gulls were established, but prior to 1996?
[2]
2.
Explain why the population of terns varies from year to year before the gulls arrived?
[3]
[3]
3a. Describe at least 3 ways that ring-billed gulls could DIRECTLY effect common tern populations.
b. Describe at least 3 ways that ring-billed gulls could INDIRECTLY effect common tern populations.
[1]
[3]
[2]
4a. Determine the carrying capacity of this environment for the ring-billed gulls, explaining your work?
b. Why would this environment have a higher carrying capacity for the gulls than it does for terns?
c. Explain what happened to the ring-billed gull population between 1986 and 1991?
[2]
[1]
5a. After 1996, the population of terns changed, explain what likely happened to the population of gulls.
b. On the graph, show the pattern for the ring-billed gulls from 1996 – 2001.
[2]
[1]
[3]
[2]
6a. To count a population of gulls, 120 birds were captured and marked. Because the gulls were molting,
they could not fly away and when a second capture was made, 98 birds were recaptured of which 17
were marked. What would be the total gull population.
b. Given that the area where the gulls nest is 1.5 km by 2.1 km, what is the population density of gulls
from 6a?
c. Allee effect
reproduction fails to equal ____________________ due to low density
eg. can not find a _________________
eg. species that rely on ‘___________________________’ can’t do so when numbers low
d. Minimum viable populations size
enough individuals so that the pop can cope with variations in __________ & ____________
eg with human help – _____________ whooping cranes was enough
eg in wild – ___________________ elephant seals was enough
for many species – ______________ are needed for this
2. Density Independent Factors
the number or density of individuals does not affect the _______________________
a. __________________ factor – one part of the life cycle that is limited and
can not be compensated for by __________________ elsewhere
eg. if seeds need 3 days of _________________ to scarify them and we have a warm winter
with no frost, ______________ grow even if it is a good Spring!
eg. DDT makes hawk ______ ______________ _______________, regardless of how many hawks
are in an area or how many good nest sites & how much food!
[work on Questions on Populations A]
Questions on Populations
A. For each of the underlined species, identify the following changes as density-dependent
OR density-independent factors on the population and EXPLAIN your reasons.
[2 marks each]
1.
2.
3.
4.
5.
6.
A few animals infected with tuberculosis are accidentally introduced into the Canadian
wood bison herd in northern Alberta.
Arsenic leaks from a mine and enters a river where crayfish live.
A pack of 15 wolves move across the border from Canada into a very large Montana park
where they find adequate food, but frequently do not find mates for several years.
Zebra mussels enter the Great lakes and grow on any surface, filtering food from
the water and being eaten by a wide variety of ducks, including scoters.
The whooping cranes in Florida are doing well with numbers over 200, but they still do not
know how to do the proper mating dance to stimulate ovulation.
Brown snakes arrive on Guam where they eat birds, lizards, nest under rocks and have no
island predators and the snakes have become a serious pest with a bounty placed on them.
B. Make survivorship curves of the three species below indicating which is most ‘r’
and which most ‘K’ –like.
[1 mark each]
Species X – 1000 seeds released at a time; mature at 6 months;
lives average of 7 months
Species Y – 10000 seeds released at a time; mature in 3 months;
lives average of 5 months
Species Z – 100 seeds released at a time; mature at 18 months;
lives average of 48 months
C. Identify and EXPLAIN which of the plant species [X,Y or Z above] will do best in the
scenarios below:
Scenarios
7.
8.
9.
10.
11.
[2 marks each]
A forest fire has just burned through an area.
An area has been left as parkland since 1925.
A beetle from Asia that strips all the leaves off plants has arrived in a Canadian
forest.
An area near a river is prone to flooding, on average, once every 7 years.
Migratory bison come through the area every second year to feed on plants.
D. EXPLAIN the type of symbiosis seen in each of the examples below
[2 marks each]
12. An acacia tree produces sugary globules that are eaten by insect-killing ants
that live inside the hollow stems of the acacia.
13. A remora sticks to the underside of a shark where it picks up scraps of food
dropped by the shark.
14. A photosynthetic alga lives inside the rigid chitin skeleton of a fungus.
15. A wasp disguises itself as an ant and enters the ant burrow where it is fed and
looked after by workers that normally feed young ants.
16. A flower has purple arrows pointing towards the nectar sacs, a beetle sees only
ultraviolet light.
D. SURVIVORSHIP and SELECTION TYPE
1. Survivorship curves – tell us how long individuals __________________ in a population
type I – species with a _______________ survival rate of their young
- most of the individuals are expected to die only when ____________________
- eg ________________________
type II - species in which individuals die at a ________________ rate from predation, disease, etc.
- eg squirrels, bees, most reptiles
type III -species with most individuals die when __________________
- _______________ babies are born, but ________________ survive very long
- eg tobacco, salmon, oysters
Survivorship curves
1000
Type
100
Number of survivors
[log scale]
Type
10
Type
0
0
20
40
Percent of life span
60
80
100
2. ‘r’ and ‘K’ selection
a. ‘r’ refers to species whose population is well ______________ the carrying capacity and
so can still grow __________________ with a rate ‘r’
b. ‘K’ refers to populations that are _____________________ the carrying capacity [K]
c. ‘r’ and ‘K’ refer to different _____________ that will ensure the_______________ of the species
d. the environment, ________ of the organism, ___________ & __________ of offspring, maturity,
_____________ expectancy and frequency of ___________________ all influence this
K
r
Unstable environment, density independent
Stable environment, density dependent
interactions
_____________ size of organism
______________ size of organism
energy used to make each individual is ______
energy used to make each individual is
_________
____________ offspring are produced
______________ offspring are produced
____________ maturity,
____________ maturity
often after a prolonged period of
_______________
___________ life expectancy
___________ life expectancy
each individual reproduces ____________
individuals can reproduce
__________________
type _______ survivorship pattern
type ___ or _____ survivorship pattern
in which most of the individuals die within a short time but
a few live much longer
in which most individuals live to near the
maximum life span
[work on questions B & C]
E. INTERACTIONS WITHIN COMMUNITIES
1. Interspecific competition
a. 2 or more species struggling for the _________ resource
b. both species will ______________
c. eg. two plants growing in the same shallow depression compete for water
& neither gets enough
2. Predation
a. one species ____________ and ____________ another
b. the predator ___________ but the prey ________________
c. but if the predator eats too ______________ prey,
then the prey ________________ & predator also _____________
____________
___________
d. note:
there is always more of the ______________
the two cycles are out of ________________ as there is a delay in the effect
as predator #’s increase, prey #’s ________; as prey #’s fall, predator #’s ________
3. Defense mechanisms
a. ____________– don’t get seen by predator OR prey
eg.
b. ____________– produce or accumulated
eg. ___________ butterfly
c. ____________- pretend to be toxic
eg. ___________ butterfly
4. Symbiosis
a. _____________ - both gain
b. ____________
eg. _____________ & giraffe
- one gains, one unaffected eg. _________ on back of turtle
c. ______________ - one gains, one loses
eg. ____________ and you
[Work on Questions D]
F. Endangered species.
Meaning of status
1. ________________ is beyond help.
2. ________________ can only be saved by imports.
3. ________________ is in serious trouble & we must act fast to save these species.
4. ________________ means we have more time before they become endangered.
5. ________________ means we need to be concerned in the future.
Causes of endangerment
1. _________________________ Once the trees are gone, everything that lived in them is gone as well.
2. _________________________ We are running out of many species of fish.
3. _________________________ The introduced starling has taken nest sites from many local birds.
4. _________________________ The pond still exists, but now few things can live in it.
Factors influencing Endangerment
a) SIZE
___________________ animals need more food and more space.
Both animal may eat a similar ________________ BUT one eats much more &
so needs to __________________ more to find more food
b) RANGE
An animal that is found in ______________ place is at risk if anything happens to that place.
The species with a _____________________ range is at greater risk
than one that is found everywhere in Canada
c) DIET
A __________________ is at greater risk because its food may become rare
more readily than a ________________________ food.
d) BIOTIC POTENTIAL
_____________ rate, survival to reproductive age, births per __________ and
births per ____________ are all part of this. eg._________ breed much faster than buffalo.
e) HUMAN INTERACTIONS Some animals do well around people and some do not
Some are killed from ______________
Some are killed by ______________
Some reduce their range by ____________________ humans.
Some are poisoned by ____________________ or purposely to kill predators.
Putting all the factors together
Species A:
small, large range, omnivore, moderate biotic potential, many human interactions
Four ____________________ & one negative factor.
Species A: _________________
Is Species A at risk?
________________________________
Species B
medium size, large range, omnivore, very high biotic potential, many human interactions
Four ____________________ & one negative factor.
Species B: ________________
Is Species B at risk?
________________________________
Predictions are not always easy
The _____________________/ human interactions involve feeding.
The ____________________ / human interactions involve killing.
BUT, in general, the more ___________________ factors,
the more _________________ the species is to be in trouble.
work on endangered species questions
HUMAN THREATS TO OTHER SPECIES
1. HUMAN POPULATION GROWTH
-humans directly compete with other species for __________ and ____________
-more humans means more ___________________
2. HABITAT FRAGMENTATION
a single large area of ___________
the same area broken up into _________
EFFECTS OF HABITAT FRAGMENTATION
- this creates barriers for _______________
- the ___________________ [ vegetation is different for the outside 10 – 30m due
to available light]
different ___________ means different food and nests
- fragmented habitat gives introduced ______________ more access to the habitat
3. HABITAT LOSS
- not all habitat is ____________
- some habitats are more _______________ than others
-these are classified as _______________ areas or Biodiversity ___________
A. WHAT ARE WILDERNESS AREAS?
-only areas greater than ______________ km 2
-at least __________ percent of original vegetation
-less than_____________ people / km 2
WHERE ARE THE WILDERNESS AREAS ON EARTH?
-there are ________ Wilderness Areas
-they include habitats on every _______________, ranging from the Amazon rainforest
to the Sahara desert
- unfortunately, most of the Wilderness areas are in the _____________
where there is ____________ biodiversity
B. WHAT ARE HOTSPOTS?
-these are the areas on Earth with the ____________ biodiversity per square kilometer
-there are _________ biodiversity hotspots
-they contain ________ percent of all plant species
and ________ percent of all terrestrial vertebrate species
-they only occupy _______ percent of the planet's land area.
WHERE ARE THE HOTSPOTS?
most biodiversity hotspots are in the ________
The Wilderness area do not _____________ very much with the Hotspots.
C. What are endemic species?
Any species ___________ found in one area is said to be ENDEMIC to that area.
These ENDEMIC species may be found only on a single _____________
or ___________________, in a single river or ____________.
Why are there endemic species?
-they are not capable of ______________ great distances to other suitable habitats
-their _________________ requirements are only met over a small area
Why do hotspots have so many endemic species?
-they have ___________ environment
-they have lots of ________________
-they have been ______________ for long times and the result is lots of endemic species
Endangered Species
1. With reference just to the chart below, EXPLAIN which species is most likely going to become
endangered AND which is least likely to become endangered.
Species A
Species B
Species C
Species D
Species E
SIZE
medium
small
medium
large
small
DIET
herbivore
carnivore
eats species E
carnivore
eats species A
omnivore
herbivore
BIOTIC
POTENTIAL
medium
low
high
high
low
RANGE
large
small
medium
large
small
HUMAN
INTERACTIONS
few
many
few
some
many
2. The map below deals only with Species E and Species B. Species E lives only in areas 1, 2 and 3 while
Species B lives only in the forest. EXPLAIN which of populations 1, 2 or 3 of Species E will survive
the best, by outlining the threats to, and advantages of, each of these populations [remember the
information from the chart above].
BRIDGE
1
ROAD
MAJOR RIVER
3
2
MINOR RIVER
FOREST
HUMAN POPULATIONS
A. History
1. Homo sapiens sapiens arose in Africa about ______________________ years BP
2. small populations moved out of Africa as _____________________________
3. birth rates were ____________, but ___________ survived childhood so population grew ____________
4. the human population was about _______ million by 12,000 BP the agriculture begun
5. stable food resources now ____________ childhood survival and so population growth ______________
6. by 2000 years BP the world population was up to ________ million,
with a doubling time of ______________ years
7. based on that prediction, there would be about _______________ million people today
8. but the rate of population growth increased dramatically due to ___________________
and __________________________ to a level 10 x that predicted number
B. Demographic Transition Models
1. pre-industrial
[diagram on next page]
- high ______________ rate, but equally high _____________ rate
- population is pretty ___________________ as little surplus food
- there is agriculture, but yields are ____________________
- eg _____________, _________________
2. transition
- agricultural surpluses people move into ___________________
as now farms can feed __________________ populations
- population starts to increase then grows ________________________
- birth rate ____________ a bit as people choose _________ to have as many children
- death rate _____________ notably due to improved hygiene & health care
-eg __________, ___________
3. industrial
- birth rate continues to ________ as more people chose ____________ families
- but death rate _________________ faster due to food & health care advances
- population continues to _________________
-eg. _____________, ________________
4. post-industrial
- birth rate ___________ even more as ________________ families become the rule
- death rate is ________________ now & population actually starts to decrease
- eg. _____________, _______________
DEMOGRAPHIC TRANSITION MODELS
C. Population Pyramids
1
2
3
post-reproductive
reproductive
pre-reproductive
1. growing population – _________young people [0-15] who will later become _______________ [15-45]
and _______________ people [45 +], so little infrastructure for elderly
eg _______________
2. stable population – __________________ numbers between 0-15 and 15-45
so current reproductive group replaced by _________________ sized group
number of elderly is ___________, but much larger than in growing population
eg. ________________
3. negative growth – ________________ young people than people between 15-45,
so a ____________________ in reproductive numbers is coming
but an __________________ in elderly
eg. ________________
4. Environmental consequences of each pyramid type
a. growing population
- currently has a ________________________ impact on the environment
- societies are in _____________ and so using _______________ amount of natural resources
- however, this society is ______________________ rapidly
and so in the future there will be a __________________ impact
b. stable population
- currently has a ___________________________ impact on the environment
- societies are ________________________ and so using ____________ of natural resources
- this society is _________________________ slowly and becoming more ______________
so in the future there will be a _________________ impact
c. Negative growth
- currently has a very ___________________ impact on the environment
- societies are _______________________ and so are using _____________
amounts of resources
- however, this society is slowly ____________________________
and so in the future there will be a _________________________ impact
1.
D. World Population
2.
_____________
revolution
1 million BP
____________
revolution
15,000 BP
1700 AD
_______________
revolution
3.
2004
0. each revolution has _________________ population, but the Industrial revolution has resulted in
_________________________ as agricultural production went up so much and hygiene improves
1. in this scenario, population continues to grow for the _________________________________
2. in this scenario, population growth ____________________ soon and stabilizes
3. in this scenario, we _______________ the carrying capacity, damage the Earth’s ability to feed us
and then the population _________________ due to famines and pestilence
eg.
soil _____________________ reduces crop yields
______________________ gases cause droughts & floods reducing crop yields
soil ___________________ reduces crop yield