lecture 3.1+3.2 Flashcards
Some islands are surrounded by kelp, while others are not. Why?
Sea urchins affect the density of kelp
What were the results from the urchin removal study?
Removal of urchins will result in higher kelp density
What is a population?
a group of individuals of the same species that live in a particular area and interact with one another
Why is hard to assertain what an individual is?
Aspen trees produce clones (genetically identical copies) when new plants grow from root buds. A grove of aspens may all be from the same individual. Clones are formed via asexual reproduction. so many can be present but population size would be 1.
What is population size?
Total number of individuals
What is population density?
total number of individuals in a given space. eg. 20 hectare island with 2500 lizards. denisty 2500/20=125 lizards per hectare
What is budding?
Type of asexual reproduction. Clonal offspring detaches from the parent. Kind of like daughter plant detaches or bud detaches
What is apomixis?
Type of asexual reproduction. Clonal offspring produced from unfertilized eggs [PARTHENOGENSIS]
What is horizontal spread?
Type of asexual reproduction. Clonal offspring produced as the organism grows and spreads laterally across an environment.
What is a genet and what is a ramet?
An individual can be defined as the product of a single fertilization. An aspen grove would then be a single genetic individual or genet.
If members of a genet are independent physiologically each member is called a ramet. eg. strawberries
What is absolute population size?
Actual population abundance (all individuals)
What is relative population size? How do we measure it?
Number of individuals in one time period or place relative to the number in another.
Count the number of an organism using the same method each year but don’t necessarily count the total number of the organism
What assumptions does relative population size make?
Assumes tight correlation between absolute and relative population sizes.
What are the two ways of estimating abundance/population size?
Area-based counts and mark recapture
When is area-based counting used to estimate population size?
when determining abundance of sessile [not free to move about/ move incredibily slow] organisms
How is area-based counting done?
Have quadrats: sampling areas of a specific size which are required to be a good representation of the entire area and are chosen at random or placed on a grid. individuals are counted in several quadrats; counts are averaged to estimate population size
How does mark recapture work?
Subset of individuals are captured, and marked or tagged then released. at a later date individuals are captured again and the ratio of marked to unmarked individuals is used to estimate population size.
When do we use mark-recapture?
when estimating a population of very mobile organism’s
What is the formula used to estimate population size when using mark-recapture?
N=(M*C)/R m=intially marked, c=captured later R=recaptured that are marked
What is exponential growth? What does the pattern look like on a graph?
when rate of growth increases (or decreases) in proportion to the current number of individuals. J-shaped pattern
What is logistic growth? What does the pattern look like on a graph?
Number of individuals increase rapidly at first and then stabilize as the population reaches carrying capacity. S-shaped pattern
What is carrying capacity?
Max population size that can be supported indefinitely by the environment. Population size often fluctuates around this number.
What are population fluctuations?
numbers increase or decrease erratically from an overall mean, often difficult to predict
What are population outbreaks?
Number of individuals in a population explodes at certain times.
What are population cycles?
regular highs and lows usually same minimum and same maximum everytime (very regular).
put mneuoposis on cheat sheet
Fluctuations in population size can increase the _________
risk of extinction
A population that fluctuates in size grows slower than one that does not vary. Why?
A fluctuating population suffers from mathematical growth constraints, resource imbalances, and extinction risks, leading to an overall slower long-term growth rate compared to a stable population.
Example:
A population of 100 increases by 50% one year (→ 150).
But if it then decreases by 50%, it drops to 75, not back to 100.
Even though the average of +50% and -50% is 0%, the population has shrunk instead of staying the same.
What is effective population size?
Number of individuals that can leave offspring to the next generation
What does the reduction of effective population size result in?
Extinciton vortex
draw extinction vortex on cheat sheet
write abt caribou on cheat sheet
