Unit B Ecosystems and Population Change

Mechanisms of Population Change

Variation among Species

All around us because it’s the differences between living things

Some give organisms a survival advantage, while others cause disadvantage, others have no bearing on survival

Variation that is advantageous=Adaptation

Variability of individuals within same species arise from mutations and sexual reproduction and passed through generations

Mutations

Mutations are the random changes in DNA Caused by chemicals, radiation or errors made while

copying Large populations over long time will have a more

substantial number of mutations Effects can be:

Neutral=no effect on reproductive success (fitness) Harmful= selective disadvantage▪ Sickle cell anemia-disorder that cause red blood cells to become

crescent shaped instead of round and smooth causing blood clots and other medical problems

Beneficial = selective advantage▪ Mutation that makes houseflies resistant to DDT in pesticides▪ California ground squirrel have mutation that makes their blood

better able to combat rattlesnake venom

Sexual Reproduction

Production of offspring by union of sex cells from 2 DIFFERENT parents and 2 DIFFERENT sets of DNA means: More traits become available because

choices of mates Different combos of genetic material Random combos of genetic material1000 males and 1000 females mean over 1

million different mating possibilities

Inherited Variations

Only organisms best adapted to their environment will survive and pass on genetic characteristics

Measuring Inherited Variation

Pg 165 Part 1 Human Variability (use data provided) Evaluation Synthesis

Pg 165 Part 2 Variations in Nature Evaluation

Evolutionary Biology

Compelling scientific theory that explains how organisms change and the diversity of species

To appreciate and judge the validity of this theory it is important to examine the evidence and review how we gain this knowledge

Major goal is to understand dramatic changes in populations over time

Evidence for Evolution

What proof is there that present day species evolved from ancestral forms?

Many lines of investigation Some direct observation and experiment, some

more indirect Gathered from

Fossil record Geographic distribution of species Comparative anatomy and embryology Behavior Plant and animal breeding Biochemistry and genetics

Fossil (Paleontology)

Species today are different from those living in the past

Progression of different species on Earth over time from simple forms in most distant past to increasingly complex forms

Radiometric dating helps scientists accurately determine ages of rocks and fossils

Living species & most closely matched fossils are typically located in the same geographic region

Biogeography

Study of geographic distribution of life on earth

Proves species evolved isolated & independent after the breakup of the continents

Unique species (endemic)

Anatomy

Homologous (similar structure different function) & vestigial (no useful function) features provide evidence of changes (pg 145)

Analogous features (similar in appearance and function but do not appear to have same evolutionary origin)

Embryonic development

Biochemistry

Compare biogeochemical characteristics

Proteins become increasingly different over time in different species

DNA sequences from different species that code for the same protein vary in number & order of 4 nucleotide basesPg 147

Artificial Selection

Process of humans selecting & breeding individuals with desired traits

Use it to produce dramatic changes in relatively short period of time

Provides evidence that this can happen over longer period of time & less dramatically

Pg 148 cabbage

Worksheets “Variation among species” and “Evidence for Evolution”

Developing Theories to explain change

How do theories explain evolution on a global scale?

Theory model that accounts for all known

scientific evidence as completely as possible

Provides plausible explanation of how things in nature are related

Helps scientists to make testable predictions

Lamarck’s Theory

Early 1800s New very simple species arose spontaneously

from non living matter (spontaneous generation) and gradually became more complex

Organisms had “force” or “desire” that lead them to change

Thought organisms acquired traits/ characteristics that were passed down the generation Giraffe got long neck over years of stretching and

wanting to reach the food

Darwin

http://www.youtube.com/watch?v=BREvUKpZTeU

http://www.youtube.com/watch?v=Hu08eiYkwAk

Darwin’s Theory

Observations#1 Individuals within any species exhibit

many inherited variations#2 Every generation produces far more

offspring than can survive to reproduce#3 Populations of species tend to

remain stable in size

Darwin’s Theory

Inferences#1 Individuals of same species are in constant struggle for survival#2 Individuals with more favorable variations are more likely to survive & pass these variations on, survival is not random (survival of the fittest)#3 Since individuals with more favorable variations contribute proportionately more offspring to succeeding generations their favorable inherited variations will become more common (natural selection)

Cheetah

Faster cheetah caught more prey, therefore stayed healthier, could better compete for mates and provided better for their young. Therefore that cheetah “survived” better and passed on the favorable trait of being fast to the future generations.

Natural Selection

Peppered Moth case study

What theories attempt to explain the pace of evolutionary change

Gradualism Theory that speciation happens

slowly

Punctuated Equilibrium Theory that species evolve rapidly

followed by a period of little of no change

Pg 160 The earth has experienced periods of rapid diversification (divergent evoltion) as well as mass extinction

How do new species form Speciation is a theory that explains how

new species form (wood bison and plains bison pg 157)

3 step process (allopatric speciation) for animals in isolation Physical barrier separates interbreeding

therefore they mutate separately Natural selection works on separate

populations and they evolve separately In time differences become pronounced and

they can no longer be sexually compatible

Worksheet “Are you fit enough?”

Do you know what you are doing quiz?

Debating Science Assignment