Descent with Modification Theme: Evolutionary change is based on the interactions between...
-
Upload
ambrose-ferguson -
Category
Documents
-
view
215 -
download
0
Transcript of Descent with Modification Theme: Evolutionary change is based on the interactions between...
![Page 1: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/1.jpg)
Descent with Modification
Theme:• Evolutionary change is based on the
interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness
Evolution = change over time in the genetic composition of a population
![Page 2: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/2.jpg)
Charles Darwin (1809-1882)
•English naturalist•1831: joined the HMS Beagle
for a 5-year research voyage around the world (stopped at: Galapagos Islands)
•1859 – published Origin of Species
•Influenced by Lamarck, Hutton & Lyell, Malthus
![Page 3: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/3.jpg)
Darwin’s Theory of Natural Selection:1. Populations produce more offspring than
can possibly survive.2. Individuals in a population vary extensively
from each other, mostly due to inheritance.3. Struggle to survive: individuals whose
inherited characteristics best fit to environment leave more offspring than less fit.
4. Unequal ability of individuals to survive and reproduce leads to gradual change in pop, with favorable characteristics accumulating over generations.
![Page 4: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/4.jpg)
•Populations evolve, not individuals.•Fitness is determined by the environment.
In summary:Natural Selection = differential success in
reproductionProduct of natural selection = adaptations
of populations to environment
![Page 5: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/5.jpg)
Therefore, if humans can create substantial change over short time, nature can over long time.
Natural Selection Artificial Selection
•Nature decides •“Man” decides
•Works on individual •Selective breeding
•Inbreeding occurs
•i.e. beaks •i.e. dalmations
![Page 6: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/6.jpg)
Evidence for Evolution1. Biogeography
▫ Geographic distribution of a species▫ Geographic, reproductive isolation
2. Fossil Record – transitional forms3. Comparative Anatomy
1. Homologous structures2. Vestigial structures
4. Embryonic Development5. Molecular Biology
▫ DNA, proteins
![Page 7: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/7.jpg)
Gill pouches
Post-anal tail
Chicken embryo
Human embryo
![Page 8: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/8.jpg)
•Darwin’s could not explain how inherited variations are maintained in populations - not “trait blending”
•A few years after Darwin’s “Origin of Species”, Gregor Mendel proposed his hypothesis of inheritance:Parents pass on discrete heritable units
(genes) that retain their identities in offspring
![Page 9: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/9.jpg)
•Frequencies of alleles & genotypes in a population’s gene pool remain constant from generation to generation unless acted upon by agents other than sexual recombination (gene shuffling in meiosis)
•Equilibrium = allele and genotype frequencies remain constant
![Page 10: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/10.jpg)
Allele Frequencies:•Gene with 2 alleles : p, q
p = frequency of allele “A ” in a population
q = frequency of allele “a” in a population Note:
1 – p = q1 – q = p
![Page 11: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/11.jpg)
Genotype Frequencies:•3 genotypes (AA, Aa, aa)
p2 = AA2pq = Aaq2 = aa
![Page 12: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/12.jpg)
![Page 13: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/13.jpg)
1. Extremely large population size (no genetic drift).
2. No gene flow (isolation from other populations).
3. No mutations.4. Random mating (no sexual selection).5. No natural selection.
![Page 14: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/14.jpg)
•If any of the Hardy-Weinberg conditions are not met microevolution occurs
•Microevolution = generation to generation change in a population’s allele frequencies
![Page 15: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/15.jpg)
1. Mutations – changes in DNA Point mutations Gene duplication
Mutation will alter or create
new alleles in a population.
![Page 16: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/16.jpg)
2. Sexual Recombination▫ Rearrange alleles into fresh combinations
every generation
![Page 17: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/17.jpg)
3. Natural selection
Douglas fir trees only release their seeds during fires. Fire rarely occurs in the river bottom of this valley.
![Page 18: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/18.jpg)
4. Genetic drift: a change in a population’s allele frequencies due to chance bottleneck and founder effect
![Page 19: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/19.jpg)
A. Bottleneck Effect – genetic drift due to drastic reduction in population size▫ Certain alleles may be over/under
represented
Northern elephant seals hunted nearly to extinction in
California
![Page 20: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/20.jpg)
B. Founder effect – few individuals become isolated from larger population certain alleles over/under represented
Polydactyly in Amish population
![Page 21: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/21.jpg)
5. Gene flow – genetic exchange due to migration of fertile individuals i.e. wind storm blows pollen to another field Reduces differences between populations Gain/lose alleles
![Page 22: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/22.jpg)
Natural selection can alter frequency distribution of heritable traits in 3 ways:
1.Directional selection2.Disruptive (diversifying) selection3.Stabilizing selection
![Page 23: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/23.jpg)
Directional Selection: eg. beak sizes of birds during wet/dry seasons in Galapagos
Diversifying Selection: eg. small beaks for small seeds; large beaks for large seeds
Stabilizing Selection: eg. average human birth weight
![Page 24: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/24.jpg)
Preserving Genetic Variation•Diploidy: inherit 2 alleles
Recessive alleles less favorable Heterozygote protection
•Heterozyote Advantage: People hybrid for sickle cell anemia protected
against malaria.
![Page 25: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/25.jpg)
•Sexual selection for mating success▫Intra (within same sex) – competition for
mate▫Inter (out) – mate choice
Darwinian Fitness : ability to survive AND reproduce AND pass on alleles to offspring
Sexual selection may lead to pronounced secondary differences between the sexes
![Page 26: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/26.jpg)
• Remember:▫Individuals are selected▫Populations evolve
• Terms:▫Population = localized group belonging to
same species▫Species = members of a population that can
interbreed and produce fertile viable offspring▫Gene pool = total combo of genes in a
population at any one time▫Fixed population = all members are
homozygous for trait (usually not the case)
![Page 27: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/27.jpg)
Speciation = origin of species
•Microevolution: changes within a single gene pool
•Macroevolution: evolutionary change above the species level▫cumulative effects of speciation over long
periods of time
Similarity between different species.
![Page 28: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/28.jpg)
Anagenesis Cladogenesis
![Page 29: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/29.jpg)
Anagenesis (“new” “race”)
• Phyletic evolution• A single species
gradually changes into a different species
• No original group left• Evolution in single
direction
Cladogenesis (“branch” “race”)
• Branching evolution• One species stays same, but
small portion leaves and changes to another species
• Gene pool splits• Original + new groups• Increase in diversity/# of
species
Two Patterns of Evolutionary Change
![Page 30: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/30.jpg)
•Proposed by Ernst Mayr (1942)•Species = population or group of
populations whose members have the potential to interbreed in nature and produce viable, fertile offspring▫Reproductively compatible
•Reproductive isolation = barriers that prevent members of 2 species from producing viable, fertile hybrids
![Page 31: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/31.jpg)
Prezygotic Barriers:▫Impede
mating/fertilizationTypes:
▫Habitat isolation▫Temporal isolation▫Behavioral isolation▫Mechanical isolation▫Gametic isolation
Postzygotic Barriers:▫Prevent hybrid zygote
from developing into viable adult
Types:▫Reduced hybrid
viability▫Reduced hybrid
fertility▫Hybrid breakdown
![Page 32: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/32.jpg)
Prezygotic barriers impede mating or hinder fertilization if mating does occur
Postzygotic barriers prevent a hybrid zygote fromdeveloping into a viable, fertile adult
REDUCED HYBRIDVIABILITY
REDUCED HYBRIDFERTILITY
HYBRID BREAKDOWN
HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION GAMETIC ISOLATION
Reducedhybrid
viability
FertilizationViable,fertile
offspring
Reducedhybridfertility
Hybridbreakdown
Matingattempt
Gameticisolation
Fertilization
Mechanicalisolation
Behavioralisolation
Temporalisolation
Habitatisolation
Individualsof
differentspecies
Types of Reproductive Barriers
![Page 33: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/33.jpg)
Other definitions of species:
•Morphological – by body shape, size, and other structural features
•Paleontological – fossil record•Ecological – niche/role in community
•Phylogenetic – unique genetic history, branch on tree of life
![Page 34: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/34.jpg)
Allopatric speciation Sympatric speciation
Two main modes of speciation
![Page 35: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/35.jpg)
Two main modes of speciation:Allopatric Speciation
“other” “homeland”
Geographically isolated
Evolves by natural selection & genetic drift
Eg. Galapagos finches
Sympatric Speciation
“same” “homeland”
Overlapping populations within home range
Subset of population isolated from parent pop. change due to:
• chromosomal changes• nonrandom mating• habitat differentiation
Eg. polyploidy in plants (oats, cotton, potatoes, wheat)
![Page 36: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/36.jpg)
•Emergence of numerous species from a common ancestor introduced into new environment
•Occurs when: A few organisms make way to new, distant
areas (allopatric speciation) Environmental change extinctions
new niches for survivors•Eg. Hawaiian archepelago
Founding
Parents
![Page 37: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/37.jpg)
When 2 splintered groups rejoin geographically:
Possibilities:1. Still one species2. Two distinct species (no
interbreeding)3. Hybrid zone
![Page 38: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/38.jpg)
Gradualism• Darwin• Slow, constant
change• Less likely
Punctuated Equilibium• Eldridge & Gould• Long period of minor
change are interrupted by short bursts of significant change
• More likely
Tempo of Evolution
![Page 39: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/39.jpg)
• Independent development of similar features between 2 unrelated species
•Similar environments•Analogous structures•Eg. wings on bees & wings on birds
![Page 40: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/40.jpg)
REMEMBER!!•Dear King Philip Came Over For Good Spaghetti•Dear King Philip Crossed Over Five Great Seas•Dear King Philip Came Over From Germany Stoned•Your own???
![Page 41: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/41.jpg)
Drosophila
Lanc
elet
Fish
Amph
ibia
nBird
Human
RatM
ouse
• Phylogeny = evolutionary history of a species or group of species
Phylogram: the length of a branch reflects the number of changes that have taken place in a particular DNA sequence in that lineage
![Page 42: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/42.jpg)
• Cladogram: diagram of evolutionary relationship of organisms▫Shared characteristics due to common
ancestry▫Uses parsimony – simplest explanation, fewest
DNA base changes for tree (“keep it simple”)
LE 25-11b
Turtle Leopard
Hair
Amniotic egg
Four walking legs
Hinged jaws
Vertebral column
Salamander
Tuna
Lamprey
Lancelet (outgroup)
Cladogram
![Page 43: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/43.jpg)
Comparison of Structures
Homology Analogy
• Results from:▫ Adaptive radiation▫ Common ancestor▫ Similar origin
• Different functions• Eg. wing of bat, human
arm, dolphin flipper
• Results from:▫ Convergent evolution▫ Different ancestors▫ Different origin
• Similar functions• Eg. wings of bird, wings of
insect
Remember:•Adaptive radiation – emergence of many species from common ancestor•Convergent evolution – unrelated species independently evolve similarities when adapting to similar environments
![Page 44: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/44.jpg)
Major events during each Era• Precambrian: microscopic fossils (stromatolites)
▫Photosynthesis, atmospheric O2▫Eukaryotes (endosymbiont theory)
• Paleozoic: Cambrian Explosion▫Plants invade land, many animals appear▫Permian Extinction (-96% species)
• Mesozoic: “Age of Reptiles”, dinosaur, plants▫Formation of Pangaea supercontinent▫Cretaceous Extinction – asteroid off Mexico’s coast
• Cenozoic: primates
Note: All end with major extinction & start with adaptive radiation
![Page 45: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/45.jpg)
Land plants
Animals
Paleozoic
Meso-
zoic
Ceno-zoic
Origin of solarsystem andEarth
41
2 3Multicellulareukaryotes
Single-celledeukaryotes
Prokaryotes
Atmosphericoxygen
ProterozoicEon
ArchaeanEon
Humans
Billions of years ago
![Page 46: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/46.jpg)
Evolution of Plants
•Non-Vascular (liverworts, hornworts, mosses) Seedless Vascular (ferns) Seed Vascular (gymnosperms, angiosperms)
•Mosses: Gametophytes = dominant form•Ferns: 1st with vascular tissue (xylem,
phloem▫wet environment (fertilization in water)▫Sporophyte = dominant form
•Gymnosperms: “naked” seeds on cones▫Conifers
•Angiosperms: flowering plants
![Page 47: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/47.jpg)
Evolution of Animals – Body Plan
![Page 48: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/48.jpg)
Evolution of Animals – Body Cavities
![Page 49: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/49.jpg)
Evolution of Animals – Development
![Page 50: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/50.jpg)
Evolution of Animals
![Page 51: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/51.jpg)
![Page 52: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/52.jpg)
Evolution of Animals•Porifera (sponge)•Cnidarian (jellyfish, hydra)•Flatworms (planaria)•Mollusc
▫Gastropod (snail), bivalve (clams), cephalopod (octopus)
•Annelid (earthworm)•Arthropods (insects, crustaceans)•Echinoderms (“spiny skin” = starfish, sea
urchins)•Chordates (vertebrates)
![Page 53: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/53.jpg)
Chordate Characteristics
![Page 54: Descent with Modification Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649ddc5503460f94ad3b7d/html5/thumbnails/54.jpg)
Phylogeny of living chordates