Download Single Generation Process Tool

Biodiversity Population Change Framework
Scales
Upper
Anchor
Level 3
Level 2
Lower
Anchor
Change in Biodiversity (How and Why it Changes)
B – Populations (e.g. Evolution)
Genetic variation for the trait
Origin of genetic variation within population is random
modification during reproduction or migration (if required by
question)
Differential survival and reproduction
Multiple generations or long time scales
Excess reproduction related to fitness is mechanism for
evolution
Separate plasticity within a genome, metamorphosis, and
changes in gene expression from evolution
Recognize environment changes over time?
Lamarckian – Some organisms change in response to
environmental pressures with traits passed down to offspring
with notion of diversity in population
Multiple generations
Excess reproduction recognized associated with fitness
Student states organisms evolve or Evolution
OR Lamarckian (multiple generations) without diversity
within population
Death recognized but provide no valid reason, often an
anthropomorphic or probability related reason
Answer includes simple statements such as they get used to
it, they adapt to the conditions, or they become immune.
No reference to diversity within the population may state
uniform population within a single generation.
Organisms purposefully change traits
All have type I survivorship curves, death not recognized
QR
Rate of Change / Rate of
growth (non-linear) (e.g.
population growth
relative to population
size)
Discrete genetic
variation vs. Continuous
genetic variation
Rate of change (linear)
(Ratio) (population
growth without reference
to population size)
Rate and proportion
(relative size)
Magnitude / size
Biodiversity Single Generation Process Tool
Ecosystems are incredibly complex and scientists have devoted many years to figuring out all the
intricate details of how populations and communities of living things change over time. BUT
before you get too lost in the details, remember that there are really only two things you have to
keep track of in order to explain how a community or population changes over time:
1. What’s there?—What types of living things make up the population or community?
2. How many?—How many of each type are there?
When we're trying to keep track of these things there are basic principles and constraints that
always apply no matter how complex the changes in population and community are. The life
cycle of any living things can be divided into two distinct phases in which these principles and
constraints apply.
a) Growth and Selection Phase –dispersal constraints, environmental constraints, and
community interactions
b) Reproductive Phase—excess reproductive capacity and descent with (random)
modification
This process tool can help you trace what's happening to population or community over a single
generation. Now we will talk about how to fill in the Single Generation Process Tool for a
population or community with two types of living things.
1. Fill in the key with the type of organisms you are looking at. Then code the
symbols in the “young” stage according to the frequency of each type present at
the start of this generation.
2. Young to Adult (growth and selection phase).
a. What will cause there to be differences in the number of living things
between the young and adult stages? Write those things in the selection arrow.
b. Will any of these things affect one type of living thing more than another?
Indicate this in the selection arrow.
c. Now code the
symbols of each type in the “adult” stage taking into
account each type present after some have died.
3. Adult to Young of the next generation (reproduction phase)
a. What will cause there to be differences in the number of living things
between the adult and young of the next generation stages? Write those things
in the selection arrow.
b. The size of the population will increase under most circumstances due to the
natural reproductive capacity of organisms; you may or may not cross off some of
the
symbols to show change. If the population size increases, then draw in
symbols to show the change.
c. Will any of these things affect one type of living thing more than another?
There may be a change due to random modification during reproduction or if
some types have more or less babies than another. Describe any changes in the
arrow.
d. Then code the
symbols in the Young of the next generation stage
according to the frequency of each phenotype present at that stage.
We will give an example about a population of brown and white mice.
Single Generation Process Tool
_____young __
_____adults______
Selection and Growth
___________________
___________________
___________________
Types of living things key:
= __________________
= ___________________
= ___________________
____young of next generation_____
Reproduction
___________________
___________________
___________________
Single Generation Process Tool
Question: How did the white color arise in the population?
_____young __
_____adults______
____young of next generation_____
Selection and Growth
Reproduction
Size reduced due to death by
predation, disease, etc.; no
change in types
Random mutation for white
color; Size increased 4
offspring per mouse
Types of living things key:
= __brown colored mice__
= __white colored mice___
= __NA_______________
Single Generation Process Tool
Question: How did the white color become more common?
_____young __
_____adults______
____young of next generation_____
v
Selection and Growth
Selection for white because of
predation ; population size
reduced due to death
___________________
Reproduction
__ No change in the
proportion of each type;
population size increased 4
offspring per mouse
_
___________________
Types of living things key:
= _brown colored mice___
= __ white colored mice__
= __ NA______________