1

Who Lives Where, and Why?

• Tolerance limits and evolution• Evolution and Ecosystems• Ecosystems/Community Properties• Communities in Transition - Succession

22Fig. 4.4

i.e. Temperature or Precipitation

33

Cold, oxygen-richwater

Can tolerate warm, lowoxygen water

4

Adaptation

• Two types of adaptation– By individuals

• Adjustment to conditions

– By population• Through genetic mutations creating new traits

• When a population adapts and a new species is created, this is evolution

– Evolution operates by Natural Selection

i.e., acclimation – dogs growingWinter coat

Survival of the fittest OR more successfulat passing on their genes

55Similar to Fig. 4.9Specialized accordingto food source

6

Evolution

• New species are created through Natural Selection, when adaptive traits make it possible for a segment of the population to survive in a different environment and/or use a new resource. – New trait created by random genetic mutations– Trait improves survival and so gets passed on to future

generations– Over time, segment of the population with new trait becomes

separated from the rest of the population and the two no longer interbreed.

– Once interbreeding ends, the two are now separate species• Number of species limited by how far the resources can be

partitioned

77

Partitioningof winter

feeding grounds

8

Evolution

• Number of species limited by how far the resources can be partitioned

• Each species carves out its ecological niche

99Fig. 4.7

Competition for resources causesevolution

1010Fig. 4.8

11

Evolution to Ecosystems

• Evolution creates new species• Species live in and compose biota in ecosystems

– Species: Small scale, adapted to a microenviroment – small spatial scale

– Ecosystems: Large scale, adapted to a macroenvironment – large spatial scale

• Ecosystems include biota (communities of organisms) and their physical environment (i.e. atmosphere/crust or ocean)

12

BIOTA: Important concepts for Environmental Science

• Community productivity• Community complexity• Community resilience• Community changes with time

13

Community Properties

• Productivity– Primary: converting solar energy to chemical

energy• Can be very productive, but not necessarily efficient

• Abundance and diversity of species– often inversely related

1414

Fig. 4.21

Energy from Sun!

15

Extremely highProductivity Systems:

Tropical rain forests

Coral reefs

16

Community Properties

• Productivity– Primary: converting solar energy to chemical

energy• Can be very productive, but not necessarily efficient

• Abundance and diversity– often inversely related

• Complexity• Resilience and stability

Will depend on communitystructure (keystone species?)and distribution of nutrients

17

Keystone Species

• Species that is key to Community structure– Analogy: Pick-up sticks are Community of

species, the stick that you pull out and they all fall down is a keystone species

18

Giant Kelp is keystone sp. on Pacific Coast of California

• Provides food, shelter and structure for whole community, affecting resiliency of ecosystem to change

• Ecosystem severely impacted when sea otters were hunted, as they ate fewer urchins, which could then eat more kelp

Fig. 4.20 – sea otters

19

Communities in Transition

• Primary and secondary succession

2020

Secondary

Primary

2121

Fig. 4.26

After Ice Age,for example

22

Pioneer Community on Hawaiian Lava

2323

2424

Kettle Lakesin glaciated regions like Minnesota

2525

Eastern trees

2626

27

Succession and Climax Communities

• Do communities always return to the same group of species?– NO– Example:– Addition of P to lake with submerged plants initially

makes plants grow more– If P gets high enough, floating communities (algae and

other plankton) shade bottom and submerged plants die– If P goes back down, submerged plants may not come

back because floating communities will remain and sediments have built up on the bottom

28

Worries for Succession in MN forests

• Global warming– Species with different tolerance limits step in– Diseases/pests more successful with warmer

climate• Invasive species

– Non-native species out compete native species and change community

– Non-native Pests challenge native species

29

The End.

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