Law 3: Everything is Always Changing Succession – How the ecosystem changes over time Natural Selection – The survival and reproduction of organisms with particular traits

Ecological Succession The gradual process of change and replacement of some or all of the species in a community. – May take place over hundreds or thousands of years – Each new community makes it harder for the previous community

Primary Succession Occurs on a surface where no ecosystem existed before No soil On rock or sand dunes Takes many years to establish an ecosystem.

How Primary Succession Happens Where? – Begins where there is no soil – Volcanic islands, areas exposed after a glacier, deserted parking lots What happens? 1.Bacteria and lichens or wind tolerant plants 2.Rock begins to break down or sand becomes stable 3.Soil begins to build up

Examples of Primary Succession Coastal sand dunes Hawaii

Sand Dunes 1.Dune building – wind causes sand to build up next to coastline 2.Pioneer stage – wind tolerant grasses begin to move in, stabilizing the sand 3.Yellow or White dune - spurges, plants with waxy, succulent leaves and horizontal growing roots, start to grow further stabilizing the sand 4.Grey dune – continuous plant cover, soil beginning to form on the sand 5.Scrub dune – small shrubs such as hawthorn that can grow in poor, sandy soil move in 6.Conifers – final stage.

Hawaii – Volcanic Island 1.Lava flows cool 2.Colonization begins immediately rate relies on surrounding areas and moisture - Kipuka – fragmented forests, surrounded by lava flow. 3.Windblown soil, seeds, spores fall into cracks 4.Organic matter builds up on top of volcanic rock allowing for shrubs and trees to move in

Secondary Succession Occurs where an ecosystem has previously existed. Occurs in ecosystems that have been disrupted by humans, animals or natural processes such as fires storms, floods, or earthquakes

How Secondary Succession Happens When? – After a disturbance – Fire, storm, flood – Old field How? – Pioneer species start the process Moss, weeds – Middle species Tall grass Wildflowers Bushes and small trees – Climax species are the end Tall trees with a dense canopy

After a Forest Fire 1.“Weeds” move in first, deep rooted plants 2.Berry bushes, blueberries, raspberries 3.Tree species that require full sunlight move in first 4.Jack pine requires fire to release seeds from cone and germinate 5.Aspen and birch trees can sprout from underground root systems

Yellowstone Fires ,000 acres were burnt Forest floor was thick and dry after a drought Grasslands returned first Aspens grew next Douglas fir and spruce Lodgepole pines last

Abandoned Farm Field 1.Grasses 2.Cedar, shrubs 3.Pines 4.Oak, Maple

Pond Succession Ponds are formed when lakes get smaller or when potholes or sinkholes are formed 1.New ponds have sandy, sterile bottoms and small water plants like duckweed and algae – Fish from lake could be present 2.Floating plants – Frogs, turtles and small fish become abundant 3.As the pond matures, bottom becomes thicker and emergent plants take hold – Bottom becomes thick with organic matter 4.Plants become thicker, pond becomes marsh – Marsh can become swamp if trees take over

Pond Succession

How does Succession Effect the Animals? Pioneer plant species favor small herbivores As the forest grows, more predators move in As succession continues the diversity changes

Natural Selection If an ecosystem changes, the animal populations have to adapt or move Only the animals with the characteristics to survive will populate the new ecosystem Animals gain new characteristics by chance genetic mutations

Examples of Natural Selection Darwin’s finches – Galapagos Islands – Similar finches on each island – The finches have a unique beak shape – Specialized for food source on it’s island Isolated species – Mountain Sheep – One species, two populations that become isolated – Dall Sheep of Alaska, Bighorn Sheep of US, Desert Sheep of Mexico and

Artificial Selection The selective breeding of organisms by humans for specific characteristics

Natural Selection and Resistance The ability of an organism to tolerate a particular chemical designed to kill it – Herbicides Roundup Resistant weeds – Pesticides Colorado Potato Beetle – Antibiotics Methicillin-resistant Staphylococcus aureus (MRSA)