Biomes
“After sleeping through a hundred million centuries we have finally opened our eyes
on a sumptuous planet, sparkling with color, bountiful with life. Within decades we
must close our eyes again. Isn’t it a noble, an enlightened way of spending our brief
time in the sun, to work at understanding the universe and how we have come to wake
up in it? This is how I answer when I am asked—as I am surprisingly often—why I
bother to get up in the mornings.” - Richard Dawkins
I. Biome Basics
A. Climate (temperature and precipitation) affect distribution of plant and animal species around the globe.
B. A biome is a large terrestrial region characterized by similar ____________________________________
C. Levels of Organization
Population – all the members of one species in an area
Community – all of the members of all of the different types of species in a region
Ecosystem – ______________________________________________________________
Biome – the ecosystem and climate in a region
D. Maps may show specific boundaries of biomes, but it’s important to remember that really biomes may not be uniform at edges,
and are often _________________________________.
E. Climate is made of both temperature and precipitation, and both are important for determining the type of biome that is found
in a region.
F. There are three levels of precipitation in a region -_________________________________________________.
G. There are also three general temperature levels – hot (never freezes), temperate (hot in summer, several months below freezing
in winter) and cold (only 3 – 4 months above freezing).
H. The combination of the three levels of precipitation with the three intensities of temperature lead to the
________________________________________________biomes found on the planet
.
Precipitation
Temperature
Cold Forest
(taiga/boreal)
Temperate Forest
Hot/Tropical Forest
(Rainforest)
Cold Grassland
(tundra)
Temperate Grassland
(prairie)
Hot/Tropical Grassland
(savanna)
Cold Desert
Temperate Desert
Hot/Tropical Desert
II. Deserts (no, not Desserts)
A. A desert is a biome with low precipitation, scattered unevenly throughout the year.
B. Usually deserts have hot days and ________________________. There is little vegetation or cloud cover to trap or store heat.
C. Desert ecosystems are one of the most fragile types of ecosystem because it takes thousands of years to recover from a
disturbance. Plant growth is very slow, there is low species diversity, and ______________________________________
because of low soil bacterial levels.
D. All deserts get very low precipitation, but there are three types based on average annual temperature
1. Hot/Tropical deserts
2. Temperate deserts
_________________________________________
E. About 1/5th of the world’s surface is a desert.
F. Hot/Tropical deserts have very few actual plants (none of the cacti/agave/succulents traditionally associated with deserts).
II. Deserts (continued)
G. Hot deserts have hard, wind-blown surfaces with lots of rocks. The sand usually has a hard crust, which can be
__________________________________________________________________
H. Dust storms are common, especially if the hard sand crust is broken by human or animal activity.
I. The Sahara desert is an example of a hot desert. Temperatures are above freezing year-round, consistently about 20 – 25 C.
J. Temperate deserts have high summertime temperatures, but have several months of freezing weather in the winter.
_____________________________________________________
K. Temperate deserts have the plants traditionally associated with deserts – cacti, agave, and other succulents.
L. The ________________________________________________________is an example of a temperate desert.
M. Cold deserts, such as the Gobi in Mongolia, only get above freezing for 6 or 7 months of the year. Antarctica is considered
a cold desert (due to lack of rainfall).
VII. Specifics of Natural Selection
___________________- the differential survival and reproduction of individuals in a population based on the traits they
posses
Natural selection may have a ___________________,
stabilizing, or ___________________ effects on the range of
traits (phenotypes) in a population
I.
a)______________________ - shifts allele frequencies in a constant direction in response to the environment
b) ______________________ - favors the most common phenotype in a population
II.
c)_______________________- favors characteristics at both ends of the range of traits in the population and operates
against intermediate forms.
VIII Non-Random Mating
To maintain genetic equilibrium, individuals in a population must choose mates at _________________.
In reality, individuals often do not do this. Instead, they may choose a mate based on mating dances, colors, or other
behaviors. This is a special type of selection called _____________________________. This results in the best males
passing on their genes with ____________ frequency than other males.
Individuals often might mate with other members of their species that are closely related to them. This promotes
________________ - mating between closely related individuals.
This increases the frequency of _________________________ in the population and reduces the frequency of heterozygous
individuals.
VIII. Speciation
_____________________ - the process by which species originate
How does speciation occur?
Sometimes barriers arise between the parts of the population and create ______________________________. Then, two or
more gene pools exist
when there was only one. If over time there is ______________________
between the two populations then selection, mutation, and genetic drift can
operate differently in each population.
III.
This can cause different traits to arise in each population. This is called __________________
When the divergence is great enough that the two populations will no longer __________________, the two population have
become different species.
_____________________ -Populations can be separated by geographic barriers. ex. mountains, rivers
Ex. The Blue-headed wrasse was separated from the Rainbow wrasse when the Isthmus of Panama was created.
___________________ - any aspect of structure or behavior that prevents interbreeding
ex. the development of different breeding seasons or different mating behaviors
Over time, two species of frog have developed different mating calls through isolation.