Module 2

characteristics of chordates

characteristics of chordates

bilateral symmetry, notochord, hollow nerve cord, pharyngeal grooves, muscular tail

lamprey and hagfish

rudimentary vertebrae not a true backbone, no jaw

gnathostomes

jaws, cartilage fish (sharks and rays) and bony fish

tetrapods

limbs with digits, amphibians

amniotes

specialized eggs to protect embryos on land, reptiles and birds

mammals

hair and milk production

primates

hands and feet specialized fro grasping, opposable thumbs, large brains and complex social behavior

early hominins

relatively small, more upright stance than other apes, skull position, pelvis and leg bone structure

homo genus

larger brain volume, increase tool use, long distance bipedal movement, decreased sexual dimorphism

neanderthals

very closely related to homo sapiens, large brains, complex social behavior and tool use, potentially interbred with homo sapiens

spieces

can reproduce to form viable, fertile offspring with each other, but not others

reproductive isolation

prezygotic- species won’t mate or form a zygote

postzygotic- species can produce offspring (hybrids) but not viable and fertile

habitat isolation

two species occupy different habitats

temporal isolation

species that breed at different times of the (day, year, season, etc.)

behavior isolation

courtship rituals and other behaviors unique to a species are effective barriers to mating

mechanical isolation

mating is attempted, but morphological differences prevent its successful completion

gametic isolation

sperm of one species may not be able to fertilize eggs of another species

reduced viability

genes of different parent species may interact in ways that impair the hybrid’s development or survival in its environment

reduced fertility

meiosis may fail to produce normal gametes, resulting in sterility, if the parent species have chromosomes of different number or structure

hydrid breakdown

first generation hybrids are viable and fertile, but offspring in the next generation are feeble or sterile

allopatric speciation

driven by geographic changes

sympatric speciation

occurs in populations that live in the same geographic area