BIO Ch. 17

Chordates

• All have a notochord:

• Include all animals with backbones

• Include all animals with a notochord, but no backbone

Radial symmetry

• The body of an animal can be sliced symmetrically along any number of vertical planes.

Bilateral symmetry

• The body of an animal can be divided by just one plane passing vertically from the top to the bottom of the animal into two halves that mirror each other.

Segmentation

a body plan in which segments repeat

• Enabled the evolution of diverse uses of

appendages

Mammals

can be divided into three broad categories, all of

which feed their offspring with milk.

Eutherians

• Offspring are nourished inside the mother’s body through the placenta.

• Offspring are born in a relatively well-developed state.

Marsupials

• Offspring are nourished by a simple placenta.

• Offspring are born less developed.

• Offspring complete development in an external pocket or pouch while nourished by milk

Monotremes

• Monotremes lack a placenta.

• Offspring hatch from an egg

Primates

• Flexible shoulder and elbow joints

• Five functional fingers and toes

• Thumbs that are opposable

• Flat nails, instead of claws

• Brains that are large in relation to our body size

Hominids

• Humans are members of the ape family.

  • We are not just closely related to apes; we are apes.

• Ape characteristics:

  • Use of tools

  • Capacity for symbolic language

  • The performance of deliberate acts of deception

Hominins

• Are a distinct branch of apes

  • “Human” branch of the ape family

• Include our extinct relatives, like the Neanderthals

• Have one or more humanlike features that set them apart:

  • Thick tooth enamel

  • Upright posture

  • Bipedal = walking upright on two legs

  • Loss of opposable toes

  • Arched foot

Q: Through natural

selection,

advantageous traits

will tend to persist in

a population over

time.

Which traits might

have been

advantageous for

ground-dwelling early

hominins?

Bipedalism (walking on two legs), enhanced tool use, and efficient thermoregulation

Q1: Through natural

selection, deleterious

traits will tend to

disappear from a

population over time.

Which traits might

have been deleterious

for ground-dwelling

early hominins?

Walking on four legs (quadrupedalism) and having opposable toes adapted for grasping trees rather than efficient ground travel

DNA from the mitochondria of Neanderthals was compared

to modern human mitochondrial DNA (mtDNA)

- Tests showed no genetic overlap between the species.

- Modern Homo sapiens did not have Neanderthal mtDNA.

- This suggested no interbreeding involving female

Neanderthals.

mtDNA:

• Is unique because it is passed down virtually unchanged from mother to child* (though new evidence shows this isn’t always true!)

• Can be tracked from one generation to another

• Can be tracked from one species to another

Q1: Why does mitochondrial

DNA show up only from your

mother?

Mitochondrial DNA comes only from your mother because egg cells contain thousands of mitochondria,

Q2: If a Neanderthal-human

hybrid was born to a human

mother and a Neanderthal

father, could you tell by

mitochondrial-DNA sequencing?

Yes, you could tell by looking at the child's nuclear DNA and specific physical features, though not through mitochondrial DNA.

Q3: If a Neanderthal-human

hybrid was born to a human

father and a Neanderthal

mother, could you tell by

mitochondrial-DNA sequencing?

Yes, you could easily tell by mitochondrial-DNA sequencing because the offspring would carry Neanderthal mitochondrial DNA. [1]

The frontal lobe of the brain is unique to human beings, and it enables us to reason like no other animal on our planet.

• But we share the following attributes with other

animals on the planet:

- Language

- Memory

- Social culture

- Emotions

- Self-Awareness

- Morality

Which of the following listed here is the smallest

unit in the Linnaean hierarchy?

a. family

b. phylum

c. genus

d. order

c. genus

Since the human female contributes the egg to

the zygote and the human male contributes the

sperm containing only DNA (and some mtDNA

that is degraded!), you have your mitochondrial

DNA from your mother. What can you receive

only from your father?

a. nuclear DNA

b. the X chromosome

c. the Y chromosome

c. the Y chromosome

The human species Neanderthal is extinct today,

but some scientists believe that most of us carry

Neanderthal DNA in our own genomes. Where

did this Neanderthal DNA come from?

a. interbreeding between Neanderthal and

sapiens at the time both species lived

together

b. a common ancestor to both Neanderthal and

sapiens

a. interbreeding between Neanderthal and

sapiens at the time both species lived

together

All chordates are vertebrates, but not all

vertebrates are chordates.

a. true

b. false

b. false