Environmental Science
Chapter 4, section 4.1
Name: ______________________________
NOTES
Kinds of Ecosystems
4.1 Forests Tropical Rainforests
 Occur in a belt around the Earth near the equator
 Always humid and warm; get about 250 cm (100 in) of rain per year
 Get strong sunlight year-round; maintains a climate with little seasonal variation in temperature.
 Ideal climate for growing plants; nourishes more plant species than any other biome (1 hectare temperate forest
contains 10 species of trees/ same area of tropical rainforest contain over 100 species)
 Soil is not rich, usually thin and poor; rapid decay of plants and animals return nutrients to soil---used up by
plants or washed away by rainfall
 Trees form aboveground roots—growing sideways from the trees, providing extra support
Rainforest: Plant Adaptations
 Plants grow in layers; trees more than 30 m (100 ft) tall form a dense canopy-absorbs at least 95% of the
sunlight
 Little light reaches below the canopy (understory); only trees and shrubs adapted to shade can grow (ex: herbs
with large flat leaves)
 When trees fall, tree seedlings adapted to grow quickly outcompete other seedlings
 Orchids and monkey ladder vines use the tall tree trunks for support high in the canopy
Layers of the Rain Forest
 There are four main layers above the forest floor: the emergent layer, the upper canopy, the lower canopy, and
the understory
 The top layer, the emergent layer, consists of the tallest trees (60-70 m); trunks can measure up to 5 m around;
they grow and emerge into direct sunlight; animals such as eagles, bats, monkeys, and snakes live in the
emergent layer
 The next layer, the canopy, is the primary layer of the rain forest; trees grow more than 30 m tall; they form a
dense layer that absorbs up to 95% of the sunlight; divided into two (upper and lower canopy); the lower
canopy receives less light than the upper canopy; epiphytes grow in upper canopy and use the entire surface of a
tree as a place to live; capture lots of sunlight, water and nutrients from the rain; most animals live in the canopy
to feed on the flowers and fruits that grow there
 The bottom layer, the understory, receives very little light; trees and shrubs are adapted grow in low light
conditions; they grow to about 3.5 m tall; herbs with large, flat leaves grow on the forest floor must be able to
grow in darker spots and get only the small amount of sunlight that reaches there; when trees fall, seedlings
from trees must grow quickly to compete with other seedlings
Rainforest: Animal Adaptations
 Incredible diversity of vegetation may have led to the evolution of the greatest diversity of animals anywhere on
Earth
 Little competition; most animals are specialists and are adapted for a specific purpose
 ex: antwrens – variety of species that eat insects at different layers; flowering plants that can be
pollinated by only one species of insect, bat or bird
 Some animals have developed elaborate methods for escaping predators; others have equally evolved methods
of capturing their prey
 ex: insects (butterfly) that looks like a leaf or twig; frogs that blend perfectly with plants;
poisons on their skin with bright colors to warn predators
Threats to Rainforests
 Used to cover 20% of Earth’s surface; today, only about 7%
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Every year tropical rainforests are stripped by logging operations or cleared for farming or cattle grazing (the
size of North and South Carolina combined)
As they disappear, so do the habitats, plants and animals become extinct
Traditions and cultures are lost as native people are displaced
Help save the rainforests by looking for rain-forest friendly products and support organizations that preserve
tropical forests
Temperate Rain Forest
 Found in North and South America, Australia and New Zealand
 Pacific Northwest is home of the only North American temperate rainforest
 300 ft tall evergreen trees (Sitka spruce, Douglas fir) dominate the forest; mosses, lichens and ferns are
abundant
 Moisture pervades everything; cool, humid forest
 Located at 48° north latitude; rarely freezes (Pacific Ocean moderates the temperature)
Temperate Deciduous Forests
 Occur between 30° and 50° north latitude; seasonal variations can be extreme and growing season is from 4 to 6
months
 Trees drop their leaves in the fall; summer temperatures can soar to 35° C ( 95° F); winter temperatures
plummet below freezing
 Deciduous forests are moist receiving 75-250 cm (30-100 in) of precipitation
 Rain and snow help decompose dead organic matter (leaves) contributing to the deep, rich soil
Deciduous Forests: Plant Adaptations
 Plants grow in layers; forest canopy is dominated by tall trees (maple, oak, birch)
 Small trees, shrubs, bushes grow in the understory
 Forest floor gets more light than the rain forest floor, thus more ferns, herbs and mosses grow there
 Plants are adapted to survive seasonal changes; seeds, bulbs and rhizomes become dormant in the ground, trees
lose their leaves
 In spring, as sunlight increases and temperatures increase, leaves re-emerge on trees, seeds germinate and
rhizomes and roots put forth new shoots
Deciduous Forests: Animal Adaptations
 Animals are adapted to forage the forest plants for food and shelter
 Squirrels eat nuts, seeds and fruits; bears eat leaves and berries, deer eat leaves from trees and shrubs; birds nest
in the tops of trees
 Birds are migratory—fly south in the winter to avoid the harsh weather; return in spring
 Animals that stay use various strategies for survival—bears and squirrels become inactive; insects enter a state
of very low metabolic activity
Taiga
 Aka: boreal forest; has rough terrain and the forest floor is sparsely vegetated
 Trees seem barren until you look up to see the green tops
 Located across the northern hemisphere just below the Arctic Circle; winters are 6 to 10 months and extremely
cold with subfreezing temperatures that plummet to -20°C (-4°F).
 The frost-free growing season may be as short as 50 days depending on the latitude; enhanced only by constant
daylight during the summer months
Taiga: Plant Adaptations
 Trees whose seeds develop cones (conifers, such as, pine, hemlock, fir, spruce) do not shed their needle-shaped
leaves; narrow shape leaves and waxy coating retain water when moisture in the ground in frozen
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The shape (pointed) of the tree helps it shed snow; otherwise the snow would crush the tree
Conifer needles (contain acidic substances), acidify the soil when they fall, preventing other plants from
growing; blueberries, a few ferns and mosses can survive the acidic soil
Climate and acidity hinder decomposition which results in slow soil formation
Taiga: Animal Adaptations
 This biome is dotted with lakes and swamps in the summer, attracting birds that feed on insects, fish or other
wetland organisms
 Birds migrate south in the winter; shrews and voles burrow underground; moose and arctic hare eat whatever
vegetation they can find; lynx, wolves and foxes eat the hare and shed their brown summer fur and re-grow a
thick white fur in the winter