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Adaptations CO 2 CALVIN CYCLE Bundle- sheath cell 3-C sugar C 4 plant 4-C compound CO 2 CALVIN CYCLE...
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Transcript of Adaptations CO 2 CALVIN CYCLE Bundle- sheath cell 3-C sugar C 4 plant 4-C compound CO 2 CALVIN CYCLE...
Adaptations
CO2
CALVINCYCLE
Bundle-sheathcell
3-C sugar
C4 plant
4-C compound
CO2
CALVINCYCLE
3-C sugar
CAM plant
4-C compound
Night
Day
Mesophyllcell
CO2 CO2
How Did Darwin Come Up With His Ideas?
• Scientific Method• Key observations
– Traits vary in a population– Most traits are inherited from parent to offspring– More offspring are produced than the
environment can support (Thomas Malthus)
Recap
• Limited resources• Overproduction of offspring• Heritable individual variation
– Therefore, survival depends partly on inherited features
Darwin’s Theory of Evolution
• In a varied population, individuals whose inherited characters best adapt them to the environment are more likely to survive and reproduce.
• Therefore, more fit individuals tend to leave more offspring than less fit individuals.
• Natural Selection is the mechanism– Reproduction (differential) is Key
Darwin’s Theory of Evolution
• Natural Selection is the mechanism– Reproduction (differential) is Key
• Fitness- degree of adaptation to a specific environment
• Adaptive if it enhances individual’s fitness
Observing natural selection
• Camouflage adaptations that evolved in different environments
A flower mantidin Malaysia
A leaf mantid in Costa Rica
Figure 13.5A
Pestacide Resistance
Pesticide application
Survivor
Chromosome with geneconferring resistanceto pesticide
Additionalapplications of thesame pesticide willbe less effective, andthe frequency ofresistant insects inthe populationwill grow
Figure 13.5B
Support for Descent with Modification
• Biogeography• Fossil Record• Molecular Biology, Biochemistry, Cell Biology• Comparative Anatomy
Biogeography
• Geographic distribution of species– Galápagos animals resembled species of the
South American mainland more than animals on similar but distant islands
– Organisms may have common ancestor
Fossil Evidence– Organisms evolved in a historical sequence
A Skull of Homoerectus
D Dinosaur tracks
C Ammonite casts
B Petrified tree
E Fossilized organicmatter of a leaf G “Ice Man”
Figure 13.3A–GF Insect in amber
Comparative Anatomy• Comparison of body structures in different species
– Homology- similar characteristics resulting from common ancestry
– Homologous structures- features with different functions but structurally similar due to common ancestry
Human Cat Whale BatFigure 13.4A
Comparative Embryology•Comparison of early stages of development among different organisms
Post-analtail
Pharyngealpouches
Chick embryo Human embryoFigure 13.4B
Molecular Biology
•Comparisons of DNA and amino acid sequences between different organisms to reveal evolutionary relationships
Table 13.4
Unit of Evolution
•Evolution acts on individuals, affects whole populations
–Populations are the unit of evolution–Group of individuals of the same species living in the same place at the same time
Unit of Evolution
• Evolution is change in prevalence of heritable traits in population through time
• A gene pool – Is the total collection of genes in a population
at any one time• Microevolution
– Is a change in the relative frequencies of alleles in a gene pool
Hardy-Weinberg Equilibrium• Frequency of alleles in a stable population
will not change over time– Very large population– Population is isolated– Mutations don’t alter gene pool– Random mating– All individuals are equal in reproductive success
• In reality, this never happens
Agents of Change
• Genetic Drift– Bottle neck affect– Founder affect
• Gene Flow• Mutation• Non Random Mating• Natural Selection
Variation•Extensive in most populations•Mutation and sexual recombination generate variation and can create new alleles.
Figure 13.11
Endangered species often have reduced variation
• Low genetic variability • May reduce the capacity of endangered species
to survive as humans continue to alter the environment
Figure 13.10
Sexual Selection
• Sexual Dimorphism• Sexual Selection- where individuals with
certain characteristics are more likely to obtain mates than others. – Intrasexual selection– Intersexual selection
Selection
• Heterozygote advantage– Balancing selection
• Ex: Sickle cell anemia
– Frequency-dependent selection• Fitness of genotype depends on frequency it occurs• Ex: mimicry
– Neutral Variation• Little to no impact on phenotype or fitness• Natural Selection cannot distinguish alleles