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Lecture 1

AN100 Lecture Notes - Lecture 1: Ultraviolet, Coastal Erosion, Keystone Species

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Amalia Philips

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studying the biosphere contributes to the study of ecology. The
distribution of living organisms on Earth is not uniform. WHY?
Why are organisms distributed in patches? Think of Canada vs Rain
o ABIOTIC factors (for uneven distribution) to consider:
1. The distribution of dry land is not uniform. There is more land in Northern
Hemisphere vs Southern Hemisphere, so we can assume there are more organisms
in the Northern Hemisphere.
2. Seasons are caused by uneven solar radiation, which is caused by the tilt of
Earth’s axis as it rotates around the sun. This means that the intensity of sunlight
is lower at higher latitudes. This accounts for temperature differences between
the equatorial habitats and your more northern or more southern areas. Radiation
from the sun is spread over more surface area at higher latitudes, so its
intensity is lower. The light rays also have to pass through more atmospheric
gases, which lowers the amount of radiation that reaches Earths surface.
3. Because of the uneven heating of the atmosphere, we have wind currents,
prevailing winds. There are areas where air rises as it warms up, then sinks as it
cools. This causes movements of air and in addition to the rotation of the earth,
these factors cause prevailing wind currents.
4. Wind currents and ocean currents can have profound effects on climate,
especially movements of water (because water has a high heat capacity). Water
can store and move thermal energy around the world. EX: The Gulf Stream ocean
current. London and North Equatorial are on the same latitude, but the climate is
milder in London because of the ocean currents that surround it. These
movements of water can really affect climate. EX: California current is cold.
5. Interactions of currents and geography influence climate. A prevailing wind
blowing over a mountain range can cause a rain shadow; which is when warm,
wet air coming off the ocean rises up a mountain range and produces lots of cloud
buildup and rain and you get a side with a wet forest, while on the other side, the
air will be dry and you will get a desert.
o Terrestrial Ecosystems’ assemblages of plants and animals: we find that similar
latitudes always have similar biomes (assemblage of plants and animals). (EX:
Canada’s pine forests are on same latitude as Siberia’s pine forests Species may not
be exactly the same, but the look of the places will be very similar. EX: Russia’s step
vs. US short grass prairie
There are many biomes in our Hemisphere.
1. Starting from the North Pole South, we have the Tundra. Tundra is a part
of the habitat that has permafrost-the soil never thaws, so there is a
permanent layer of frozen soil. Since water doesn’t drain in the soil, when
snow melts, it just puddles and the ground stays wet, boggy. Therefore, not
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many trees grow in the Tundra because their trees can’t dig down. There are
mainly sedges, small willows and marshy plants. There are lots of insects
and few animals.
2. Moving South, you encounter - Coniferous Forest.
3. Moving further (east of the Mississippi River), you encounter-Temperate
Deciduous Forest. In the North there are Sugar Maples in these forests
while in the South there are Hickory and Oak trees.
4. (west of the Mississippi River), you encounter-Tall Grass Prairie
(Temperate Grassland)
5. (further west), you encounter-Short Grass Prairie (Temperate
The assemblages of plants in these terrestrial ecosystems determine what
types of animals live there. Furthermore, the assemblage of plants is
determined by a combination of temperature and rainfall.
1. The two plants have very similar morphology because they recently evolved from
a common ancestor.
2. They have become adapted to similar habitats by natural selection.
D (F,T)
o A combination of amount of rainfall and average temperature is what
determines these biomes and makes them different from each other. (EX: low
temp all year- Tundra. lil warmer, low rainfall-Coniferous Forest. high temp, high
rainfall-Tropical Rain Forest. warm, low rainfall-Warm Desert)
(**stopped this lecture to do Biomes Video**)
o The largest, easily recognizable subdivisions of the biosphere are called
biomes. Each biome is characterized by a particular general type of
plant and animal community. These communities look much the same
wherever the biome occurs, but the particular species making up the
biome vary from place to place. This suggests the plants and animals
have adapted in similar ways to the environment. A biome is a collection of
similar and related ecosystems.
o 3 ways to look at a biome:
1. A biome is the largest subdivision of the biosphere.
2. It is a type of ecosystem or community shaped by a particular
combination of climate and topography.
3. A biome is a collection of smaller, similar, and related ecosystems.
1. TUNDRA adjoins the artic regions and North America and Eurasia.
beautiful, dotted with lakes and streams, mosses, sedges, willows.
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cold and frost shape the landscape. under 3 feet, its only permafrost. the
layer of permafrost prevents the penetration of liquid water into plant
root, so the vegetation is sparse.
as a result, the Tundra appears waterlogged, in spite of relatively light
Caribu is the dominant herbivore in the Tundra of North America while the
Reindeer fills this role in Eurasia. other animals are the muskox, wolverine,
artic fox, lemming. their activity is geared for short summers and long
winters. many of the animals posses extra fax and fur levels. some change
color in season.
the food chains of the Tundra are simple and limited because of the low
amount of plants and animals involved. Because animals man rely on one
particular plant or species, population of animals in the Tundra show
extreme oscillation in numbers. Owl (predator) will oscillate with lemming
2. ALPINE TUNDRA occurs on high mountains in the temperate zone.
alpine forget-me-nots grow 11,000 ft in Rocky Mountain National Park.
the marmot is an inhabitant of the Alpine Tundra.
3. NORTHERN CONIFEROUS FOREST stretches across North America and Eurasia
and is just south of the Tundra.
occur in mountainous areas like cascades, rockies.
summers are cruel and winters and cold, and rainfall is moderate.
dominant plants are evergreen trees, pine, fern. because the forest floor is
shaded year round, the forest floor is usually very bare.
animals are adapted for life in the cool forest; squirrels, beaver, porcupine
depend directly on trees for food and shelter. black-tail deer, black bear,
bobcat, wolf and moose, dwell in the ecosystem that make up the forest,
a biome is not just a single homogenous community. it consists of
smaller, related ecosystems. the Northern Coniferous Forest consists of
many types of forest that are often very near to one another. along with
many different types of forests, creeks and rivers may also be a part of this
biome. Ecological succession could turn these lakes into land then into trees
over time.
even though redwood trees are coniferous, they are not a part of the
Northern Coniferous Forest biome.
4. MOIST CONIFEROUS FOREST stretches from Alaska to Northern California.
the Pacific Ocean moderates temperatures, cooling in the summer and
warming in the winter. masses of air moving in from ocean deposit
moisture in the form of rain or fog. these forests can get 200 in rain a year.
unlike the drier, colder Northern Coniferous Forest, the understory
vegetation in this forest is good because light can filter through to the
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