CHAPTER 3. Ecosystems continually change over time

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1 CHAPTER 3 Ecosystems continually change over time

2 Great Green Wall of China Because of overgrazing, deforestation, and drought China is faced with a growing problem of the Yellow Dragon This is sand blowing and expanding sand dune in China A 4500-km-long strip of forest is how they are trying to combat the expanding sand dunes

3 HOW CHANGES OCCUR NATURALLY IN ECOSYSTEMS Chapter 3.1

4 Always Changing... Abiotic (non-living) and biotic (living) factors can change the conditions of an environment/ ecosystem Animals and plants ADAPT in order to survive in their environments. Let s look at an example (the 3-spine stickleback)

5 Three-Spine Stickleback Originally an ocean-dweller (only lived in salty ocean waters) in the northern hemisphere 13,000 years ago, the glaciers around BC retreated and some ocean water became lakes (freshwater).

6 The Sticklebacks in the lake adapted! As the salt water slowly changed to freshwater, the stickleback adapted. Now there are marine and freshwater species. Marine (left) and freshwater (right) guarding nests...

7 The Sticklebacks in the lake adapted! In six shallow lakes in BC, pairs of stickleback species developed. Bottom feeding (chunky body) Open-water stickleback They both have different physiological and behavioural adaptations to their environment

8 Question! Did the stickleback adapt to an abiotic or a biotic change in its environment?

9 In the lakes... Sticklebacks in BC lakes have evolved into species pairs (one species lives and feeds at the bottom, the other species lives and feeds in surface waters) Bottom dweller What differences do you see? Surface dweller

10 In the lakes... There are about 6 species pairs of sticklebacks in lakes around Vancouver Island. Recently, 1 species pair or sticklebacks living in Hadley Lake (Lasqueti Island) has disappeared Introduction of catfish to the lakes

11 Natural Selection Survival of the fittest Species that are best adapted (fittest) will reproduce and survive. Fit doesn t mean in shape but having characteristics that give species an advantage!

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13 Famous Example Charles Darwin Galapagos Island Finches 13 species have radiated out from one common ancestor. They occupy different niches

14 Evolution in the Galapagos Video

15 How Ecosystems Change over time Abiotic factos change in an ecosystem Biotic factors (who lives there) changes too Scientists define Ecological succession to refer to changes that take place over time in the types of organisms that live in an area Two types: Primary and Secondary

16 Primary Succession Occurs in an area with NO SOIL exists (ex: bare rock) Natural events like retreating glaciers scrape rocks Volcanoes and new rock Wind and rain carry spores for lichen that grows on rock Formation of soil Lichen die and provide organic matter to soil This process can take hundreds of years

17 Primary Succession

18 How it starts... Wind/ rain carry spores (lichen) to rocks Lichens release chemicals into rock (obtain nutrients, break down rock)

19 And then... Spores of plants (mosses) deposit Pioneer species are species that first survive and reproduce in an area, like lichens and other plants Provide food, water, nutrients

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21 Mature Communities The process of primary succession leads to the development of a mature community, which is sometimes called a climax community Ex: Boreal forest, grasslands, rainforest... These climax communities, can change too... Small disturbances cause these communities to change (even if they appear unchanged).

22 Secondary Succession After a forest fire, not much is left except ash and the burnt trees Secondary succession will occur soon after a disturbance. This is because it was once the home of living organisms. It occurs much faster than primary succession

23 Faster than Primary succession (decades to a hundred years) Why is it faster??? - Because soil with nutrients is already present

24 How Natural Events Affect Ecosystems Other natural events can cause disturbances to different ecosystems and can result in secondary succession These include: Flooding Drought Tsunamis Insect Infestations

25 Other Natural Events Flooding Can be part of normal cycle or heavy rainfall Soil erosion Soil pollution Tsunamis Caused by large earthquakes or underwater volcanic eruptions Food webs destroyed Salt water onto land and soil

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27 Erupted Aug 27, 1983 Eruption was heard in Madagascar, Philippines and Australia. Produced 40m waves. Eradicated all life on the island Now a diverse, rich rainforest

28 Other Natural Events Drought Recurring event in many parts of world Below avg precip Climate change contributes Insect Infestations Mountain pine beetle Younger trees and resin Symbiotic relationship between beetle and blue stain fungus causing more damage!

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