Transcript this powerpoint

3.1 How Changes Occur Naturally in Ecosystems
1. ORGANISMS CHANGE
• An organism belongs to a species, but is also born with unique
characteristics.
 E.g., humans have different eye colours and heights
• Sometimes the unique characteristics give the individual an
advantage.
 E.g., a salmon with a slightly larger tail may be able to swim a little faster or
farther in a river.
• Natural selection is the process wherein advantageous characteristics
grow more common in a population,
because individuals with that characteristic
are more likely to survive and reproduce.
E.g., the larger-tailed salmon will survive better
and spawn better, and the offspring have more
chance of having a larger tail as well
See pages
108 - 109
• Birds on the Galapagos Islands, off the coast of Ecuador, appear to
be products of natural selection.
 There are thirteen species of finch on the islands, and they are very similar
Galapagos
 It is believed that all species started as a single species that
finches
was changed by natural selection – finches in one area
changed in one way, finches in another area changed in
another way, etc.
 Each species has unique characteristics that allow it to
them
thrive in its own niche, and not compete with other species
for resources.
• Adaptive radiation is when many species, inhabiting
different niches, are thought to have developed from
one common ancestor.
See page 110
2. ECOSYSTEMS CHANGE
•
Ecological succession = the changes in
biotic characteristics in an area over time.
BIOTIC = living
ABIOTIC = non-living
 Two types of ecological succession:
primary succession and secondary succession
•
Primary succession - begins with nothing but bare rock
STAGES:
1.
Bare rock
 E.g., glacier scrapes away surface layer
 E.g., lava from volcano cools
2.
Lichens (a fungus & algae combined)
 Do not need soil; secrete chemicals that break rock down
 Spores carried to the area by wind & rain
 Pioneer species = the first organisms to live in an area
See pages 111 - 113
3.
Soil formation begins
 from lichen breaking down rock
 from dead lichens decomposing
 from natural weathering processes breaking down rock (wind, rain,
landslides)
 Soil may take hundreds of years to accumulate
4.
Mosses
 Can grow in little soil and nutrient-poor environments
 Add more nutrients to the soil when they die and decay
5.
Small plants
 There is enough soil built up
 Grasses, wildflowers & shrubs
 Greater variety of insects, micro-organisms and small animals
See pages 111 - 113
 Add more organic matter so soil layer increases
6.
Deciduous trees = trees with
Sun-tolerant trees
leaves, not needles. These trees
 e.g., deciduous trees
shed their leaves in winter.
 seeds brought by wind, water or animals
 greater diversity of species, including larger animals
 trees produce shade under them, which produces new abiotic conditions
• cooler temperatures
• moister soil
Coniferous trees = trees with
7. Shade-tolerant species
needles (and cones). These trees
keep their needles in winter.
 E.g., coniferous trees
6.
Deciduous trees = trees with
Sun-tolerant trees
leaves, not needles. These trees
 e.g., deciduous trees
shed their leaves in winter.
 seeds brought by wind, water or animals
 greater diversity of species, including larger animals
 trees produce shade under them, which produces new abiotic conditions
• cooler temperatures
• moister soil
Coniferous trees = trees with
7. Shade-tolerant species
needles (and cones). These trees
keep their needles in winter.
 E.g., coniferous trees
 Eventually they grow taller than the other trees and take over
 A mature forest has developed
• will remain largely the same over time (only slow or small changes)
• Called a climax community
 Primary succession occurs similarly in all parts of the world.
 Climax communities include boreal forests, rainforests, grasslands, deserts
• Secondary succession – occurs after a major disturbance in an area
that already has soil and once had living organisms.
 forest fires are the most common reason
 The soil remains…
 providing for plant growth
 containing seeds, micro-organisms, earthworms and insects
 much more rapid than
primary succession
 only lasts decades
See page 114
• Natural events affect ecosystems
1. Forest Fires

Already discussed
2. Flooding
 Can be caused by:
• Heavy rainfall
• Increased run-off from snowmelt
• Tsunamis
• Natural cycles
 Possible effects on ecosystem:
• soil erosion
• soil pollution (if toxins in water)
• spread of disease (if harmful bacteria in water)
• Natural events affect ecosystems
3. Tsunamis
= a huge, rapidly moving ocean wave
 Usually caused by large earthquakes or underwater volcanic eruptions
 Effect on ecosystems:
• Destruction of plants & animals
• Large volume of salt added to soil
4. Drought
= when an area receives a lower than average amount of rainfall over a long
period of time
 Effect on ecosystems
• plants & animals die
 Often, ecosystem can recover when it rains again
See pages 115 - 116
• Natural events affect ecosystems
5. Insect Infestations
 Many insects play important roles in their ecosystems
 Even insects that appear destructive, such as the mountain pine beetle, actually
play a role in the renewal of the forest
 When normal conditions are changed, insect infestations can occur.
• E.g., a warmer climate in BC  not cold enough to kill the beetle larvae
• E.g., suppression of forest fires  beetles able to spread more effectively
 Negative effects of pine beetle on BC forest ecosystem:
• Pine tree populations devastated
• Bird and mammal nests lost
• Human forest industry
SUCCESSION DRAWING
ACTIVITY:
You will take a piece of 8.5 x 14 blank paper and
fold it into 8 squares.
You will select an ecosystem from the next slide
and draw out succession changing that ecosystem.
OPTION 1: Pond Succession
How a POND might naturally FILL IN over
time, becoming an area of shrubs.
OPTION 2: Ocean Sand Dune Succession
How SAND DUNES might naturally acquire
soil/nutrients and turn into a forest.
1. Micro-organisms carried by wind and insects are
deposited in the pond water.
1. On the sand dunes near the ocean, nutrients begin to
accumulate from decaying seaweed.
2. Micro-organisms die and form a layer of material on
the pond bottom, filling the pond in a little bit.
2.The decaying seaweed creates soil over time.
3. Fish and other animals carried by streams, birds, and
other animals move in.
3. Grasses that can tolerate salt spray from the ocean
begin to grow in the soil.
4. The death of larger organisms provides more organic
matter on the pond bottom, filling the pond in a little
more.
4. Grasses help anchor the soil so it doesn’t blow away
with ocean winds.
5. Water plant fragments such as pond lilies and cattails, 5. The soil is now stabilized and can hold water, so other
transported by birds and wind, take root in the material
vegetation such as lichens and mosses begin to grow
on the pond bottom.
on the dunes.
6. When the pond lilies and cattails die off, they create
more organic material on the pond bottom, filling in the
pond even more.
6. As the soil layer thickens, shrubs can begin to grow in
it.
7. Water becomes so shallow that grasses and shrubs
move in. The pond is gone!
7. A forest of coniferous white spruce trees eventually
grows. The sand dunes have been replaced by a forest!
*Mandatory
assignment
Title Box: Write POND SUCCESSION or
OCEAN SAND DUNE SUCCESSION.
Also your name, date, & block.
4.
*DUE NEXT CLASS!
1.
2.
3.
5.
6.
7.
Write the 7 steps of succession at
the bottom of each square as
CAPTIONS
/15
Fill the rest of the box with a drawing showing what
is happening to the pond or sand dune at that
stage. Colouring is NOT REQUIRED. Drawings
should be done in PENCIL, NOT PEN.
IF FINISHED SUCCESSION
COMIC…
• Hand it in this class
• Work on Workbook 3.1
(p.40-43)