Name__________________________2^nd exam, bio 44, April 7, 2003

Answer all questions, 5 point seach.

1. How do we think eukaryotic cells came into being?

A symbiosis between several prokaryotic cells – one becomes mitochondria, another the chloroplast, plus infolding of outer membrane to form nuclear membrane.

2. We usually think that simple systems are primitive and more complex systems are advanced or derived. When in evolution might this not be true?

Parasites are often simpler than their ancestors.

3. What are the main differences between protostomes and a deuterostomes.

Which opening of digestive system becomes the mouth, method of cleavage, whether cleavage is determinate or indeterminate, method of forming mesoderm.

4. How is the acceptability of a classification determined.

For species – first name used is correct. For all other categories, acceptability is based on how many scientists use the classification. There is no correct, only most often used.

5. Each of the following structures serves an important function for the organisms that possess them. Tell who the ancestors of the groups that developed these structures were and why these structures were not necessary for them to survive.

a) vertebrate lungs.

Lungfish and relative developed lungs as an auxillary breathing device in stagnant fresh water. Their fish ancestors lived in the ocean and flowing water where oxygen is more plentiful and gills were sufficient for respiration.

b) flowers

flowers attract insects which spread pollen, without insects, the ancestral plants (pines – gymnosperms) had to produce a lot of pollen and rely on the wind to get it to the proper place

c) brain

needed when bilateral organisms developed – a front end with the sense organs. The ancestors were radially symmetrical (jellyfish)and needed no head end = concentration of nerves.

d) pollen

airborn male reproductive cells. Ancestral plants (ferns) use motile sperm in water

e) stomata

openings in leaves to designed primarily to prevent water loss. Ancestral group – liverworts, live in wet areas and don’t have to worry about water loss.

6. How do annual and perennial plants adapt to each of the following problems.

a) Desert conditions

Annual – avoid bad conditions, grow fast, and sense when conditions are good

Perennial – develop ways to store water and prevent its loss.

b) Fire

annual – survive as seeds buried in insulating ground.

Perennial – regrow from root or have thick fire resistant bark.

7. What are archea (archebacteria) and why are they of interest?

A group of bacteria that use sulfur and other compounds as an energy source. They share many features with eukaryotes rather than with other bacteria.

8. What is an “organizer” in development and how does it work?

An organizer is an area (group of cells) in the embryo that tells surrounding tissue what to do by secreting hormones that affect the dna, development of these cells.

9. Among vertebrates or Chordates, which organism developed each of the following and what function did it originally serve?

Bilateral symmetry

First found in larval tunicates – allowed swimming to make dispersal more effective.

Lungs

First found in lungfish and relatives – allowed breathing in stagnant water.

Feathers

First found in dinosaurs – used for temperature regulation (insulation)

jaws

first found in primitive fish – allowed mouth to close – were originally part of gill structures.

gills

first found in amphioxus like organisms – served as a filter feeding device.

nerve cord.

First found in larval tunicates – coordinates tail movement for swimming.

10, What is meant by the phrase “brushpile evoutionary pattern” and what problem does it pose for classification?

It refers to a pattern where lots of organisms arise at about the same time. This occurs when a new way of life is found (fish, birds, etc.) Since all groups arise at the same time it is hard to tell which is ancestral or to put them in a sequence.