How Changes Occur Naturally in Ecosystems Chapter 3.1

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)

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

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...

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

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 Surface dweller What differences do you see?

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

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

Natural Selection Species that are best adapted (fittest) will reproduce and survive. Fit doesn’t mean “in shape” but having characteristics that give species an advantage!

Famous Example Charles Darwin – Galapagos Island Finches A number of different species have “radiated out” from one common ancestor to inhabit different niches.

How Ecosystems Change Abiotic factors change in an ecosystem Biotic factors (who lives there) changes too Ecological Succession = changes in the types of organisms over time Primary and Secondary

Primary Succession Occurs in an area with NO SOIL (ex: bare rock)

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

And then.... Spores of plants (mosses) deposit “Pioneer species” can survive harsh conditions. Provide food, water, nutrients

Climax Community This is a “mature” community Ex: Boreal forest, grasslands, rainforest... They change too... – Small disturbances cause these communities to change (even if they appear unchanged).

Secondary Succession The slow process of plants/ animals inhabiting an area that was DISTURBED but already had soil. It was once the home of living organisms.

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

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

HOW NATURAL EVENTS AFFECT ECOSYSTEMS  Flooding Soil erosion, soil pollution if chemicals present in floodwater  Tsunamis Wave carries away or destroys plants and animals, salty soil  Drought Crop failures, livestock deaths  Insect Infestations Ex: Mountain pine beetle, bird and mammal nests lost, forest- dependent economies affected