Download - 13 The Changing Biosphere
13 The Changing Biosphere
When we finish this chapter you should be able to:Define natural selectionExplain how geographical isolation and reproductive isolation lead to the evolution of new speciesDiscuss how mutations increase diversity
13.1 Clues from the past: The fossil record
Biosphere is constantly changing (slowly)Abiotic: Geologic and Atmospheric (climate) changes
ex: oxygen added to atmosphere over timewarming and cooling cycles (ice ages)
Biotic: Fossil record shows how a organisms have changed over time. Evolution
Old species become adapted (evolve) to new conditions or become extinct. Ex: dinosaurs
New species arise under new climate conditions to replace old
Ex: Horse: from forest browser to grassland grazer
Well adapted species can survive for long periods of time
Ex: Opossum – only marsupial (pouched) animal left in N. America
Living fossils – well adapted species survive unchanged for long periods of time
Ex: Coelacanth (lobed fin fish) unchanged for 100 million years is missing link between fish and four legged animals (amphibians, etc.)
13.1 Section Review
1. Describe some of earth’s ongoing changes that affect the abiotic part of the biosphere
2. Compare the composition of earth’s primitive atmosphere with our present-day atmosphere
3. How does horse evolution show adaptations to a changing environment
13.2 Evolution through Natural Selection
Population- organisms of a species – that interbreed in nature
Members have Variations: differences in their traits due to their different genes, that help them survive and reproduce
Over production (compared to limited resources - food, etc.) leads to natural selection of best adapted ones, to pass on their genes
Adaptations – traits which help an organism to survive – new traits arise through mutation: change in the genes
Pandas thumb
Isolation - New species arise when some of the individuals become isolated and stop interbreeding with the rest
Geographic isolation – separation of a population by mountain range, river, etc.separated group changes differently from original group
ex: grand canyon: Abert squirrel and kaibab squirrel (north rim)
Leads to Reproductive Isolation(new species can’t breed with old)
Convergent Evolution
Different animals adapted to similar lifestyles
ex: mouse deer (goat)
agouti (rodent)
royal antelope (deer)
each is small, brown
– live in tropical rainforest
Also Auk (north pole)
and penguin (south pole)
13.2 section review
1. Explain how natural selection is similar to people breeding animals.
2. List 3 adaptations that help mammals, like us, survive in their environment.
3. Compare the terms geographic isolation and reproductive isolation.
4. Explain convergent evolution by comparing fish and whales
13.3 diversity and mutations
Gene pool – the collection of all variations for different genes for traits in a population – get mixed during sexual reproduction
Mutation – change in a gene, creates new or variation in traits- only mutations in egg cells can be passed on - usually negative and fatal – occasionally beneficial
Peppered Moth
England / Industrial revolution
– darkening of trees from soot
Moth population evolved from light color to dark color over 100 years.
(Now evolving back)
Quechua Indians of the high Andes in S. America have larger lungs, and more red blood cells to carry O2 in the thin air at high altitude
In what type of environment would webbed feet be an advantage?
Human Adaptation
Rate of Evolutionary ChangeTwo theories:Gradualism – gradual changes over a long
period of time.Vs.Punctuated Equilibrium – long stable periods
with brief periods of changes (1000 years)
How would climate change contribute to these?
Preserving Diversity Greater diversity (variety) in traits allows
populations to adapt to changes, rather than become extinct.
Ex: Cheetah – endangered with little genetic diversity - one disease could wipe out entire species
Ex: Depleted Fish stocks – due to overfishing – cod, blue-fin tuna, swordfish
Avoid also – grouper, snapper, Chilean sea bass
Better – salmon, mahi-mahi, tilapia, striped bass, halibut
13.3 section review
1. How do mutations affect species diversity?
2. What role do mutations play in natural selection?
3. Describe the main difference between gradualism and punctuated equilibrium
4. What can you do at the supermarket top preserve the diversity of the marine ecosystem?