Biomes
A biome is a major region that is characterized by its climate, soil types, and the dominant organisms living in the area.
Types of Biomes
1. Tropical & Temperate Rainforest
2. Desert
3. Grassland
4. Deciduous forest
5. Tundra
6. Boreal forest
An area’s biome is determined mostly by its climate
Latitude and Altitude
• Higher A, colder
• Farther L, north/south of the equator, colder
1.1 TROPICAL RAINFORESTS
- Contain over half of the world’s plant and animal species
- CA, SEA, P, NG
- Found in regions close to the equator
- Warm and humid all year long.
- Lots of precipitation.
- Diverse plant growth.
1.2 TEMPERATE RAINFORESTS
- “Temperate”= having moderate temperatures.
- Northwestern coast of U.S.
- Receives more than 300 cm of rain per year.
- Huge trees: Cedars, Redwoods, Douglas Firs
- Trees in the rain forest form several layers…
- Canopy: A leafy roof formed by the tallest trees.
- Understory: A second layer of shorter trees and vines.
- Understory plants grow well in the shade formed by the
canopy, but the forest floor is nearly dark and only a few
plants live there.
2. DESERTS
- An area that receives less than 25 cm of rain per year.
- Some deserts receive NO precipitation at all
- Deserts often undergo large shifts in temperature during the course of a day.
- Has little or no vegetation
- Located on the dry side of the mountain ranges
- The scorching Namib desert in Africa cools rapidly after the sun goes down.
- The Gobi desert in central Asia is cooler and even experiences freezing temperatures in the winter.
- Saguaro Cactus: Stem expands to store water.
- Gila monster spends weeks in its cool, underground burrows.
3. GRASSLANDS
- An area that is populated mostly by grasses and other non-woody plants.
- Receive 25 to 75 cm of rain per year.
- Fires and droughts are common.
Savanna: Grassland that is located closer to the equator
Savannas can receive as much as 120 cm of rain per year.
Grasslands are home to many of the largest animals on Earth.
Examples: Grazing by these large herbivores helps to maintain these grasslands.
4. DECIDUOUS FOREST
- Trees that shed their leaves and grow new ones each year (Oaks, Maples…)
- Receive enough rain to support the growth of trees and other plants (at least 50 cm per year).
- Growing season is 5 to 6 months long.
5. BOREAL FOREST (taiga)
- Mostly contains coniferous trees (trees that produce their seeds in cones and have leaves shaped like needles). Ex. Fir,
Spruce, Hemlock…
- Very cold winters (a lot of snow).
- Warm and rainy summers.
- Coniferous
- growing season is very short
- nearly constant daylight in summer
- includes lakes and swamps
6. TUNDRA
- Extremely cold and dry biome.
- Usually receives NO more precipitation than a desert biome.
- Most soil is frozen all year long (permafrost)
- During summer, the top layer of soil thaws, but the rest remains frozen.
- can be found in Antarctica, NP, NAC
- grass, lichens, herbs
- very short, warm season -- > insects
- Because water cannot soak into the permafrost, there are many shallow ponds and marshy areas of the tundra during the
summer
The doctor got dizzy today, boss
Population
- A population is a group of organisms from the same species occupying in the same geographical area.
- This area may be difficult to define because:
- A population may comprise widely dispersed individuals which come together only infrequently, e.g. for mating.
- Populations may fluctuate considerably over time.
- Populations are dynamic and exhibit attributes that are not shown by the individuals themselves.
- These attributes can be measured or calculated and include:
- Population size: the total number of organisms in the population.
- Population density: the number of organisms per unit area.
- Population distribution: the location of individuals within a specific area.
- The study of changes in the size and composition of populations, and the factors influencing these changes, is
population dynamics.
- Key factors for study include:
- Population growth rate: the change in the total population size per unit time.
- Natality (birth rate): the number
of individuals born per unit time.
- Mortality (death rate): the number of individuals dying per unit time.
- Migration: the number moving into or out of the population.
- Migration is the movement of organisms into (immigration) and out of (emigration) a population.
- The number of individuals per unit area) is termed the population density.
- At low population densities, individuals are spaced well apart. Examples: territorial, solitary mammalian species
such as tigers
- At high population densities, individuals are crowded together. Examples: colonial animals, such as rabbits, corals,
and termites.
- Environmental resources are finite. Competition within species for resources increases as the population grows. At
carrying capacity, the area can support its largest population.
- When the demand for a resource (e.g. water, food, space, light) exceeds supply, that resource becomes a limiting
factor.
- Animals compete for resources such as water (left) or mates (right), especially when these are in short supply or
access to them is restricted.
Limiting Factors
- Physical (or abiotic) factors
✓ temperature
✓ precipitation
✓ Acidity
- Catastrophic events
✓ floods and tsunamis
✓ fire
✓ drought
✓ earthquake and eruption
Population Growth
• Population depends on the number of individuals added to the population from births and immigration, minus
the number lost through deaths and emigration.
• This can be expressed as a formula:
Population growth =
- Births, deaths, and net migrations determine the numbers of
Births – Deaths + Immigration – Emigration
individuals in a population
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(E)
Determining population size
- Direct observation - counting all the members within a
population
- Indirect observation – observing signs of organisms ex. Nests
- Sampling – estimating the population size, counting the number of organisms in a small area and multiply to find the
number in a larger area
- Mark and Recapture – capturing animals and marking them with a radio collar, or tag and releasing them to be
recaptured later
Problems on Population Growth
• Food Shortage
• Water Shortage
• Habitat
• Health Problems
• Pollution
( for humans)
Unemployment
Peace and Order
