Exam 2: Fossil Record, Past Forests

Front 1

progymnosperms

Back 1

• appear in the Carboniferous Period of the Paleozoic Era
• 􏰂first plants to have a vascular cambium
• 􏰂first woody plants: first to be able to grow continuously in diameter 􏰂
• larger diameter allowed them to grow taller than their predecessors, but... 􏰂
• they still reproduced by spores, not seeds
  

Front 2

the rise of gymnosperms

Back 2

• first seed plants
• all plants preceding them reproduced by spores

- these plants had free-living gametophyte generations with sperm that had to swim to the egg in the open

• first plants with gametophytes completely dependent on sporophytes

Front 3

why was the fact that gymnosperms were the first plants with gametophytes that were completely dependent on sporophytes advantageous?

Back 3

because gametophyte and gametes were no longer out in the open, they were now protected by the sporophyte and actually "parasitic" on the sporophyte

Front 4

reproduction in gymnosperms now

Back 4

• now happens inside protective cone
• female gametophyte now inside the ovule

- still large in gymnosperms (surrounds embryo)

- just one cell (embryo sac) in angiosperms

• male gametophyte is germinating pollen grain

Front 5

where did the gametophyte generation go in trees and other higher plants?

Back 5

gametophyte generation became "parasitic" on (and protected by) the sporophyte generation in gymnosperms and angiosperms

Front 6

rise of conifers

Back 6

first appear in Permian Period of Paleozoic Era

Front 7

rise of angiosperms

Back 7

• large gymnosperm forests arise in Mesozoic Era, followed by...
• severe dieback of conifers and other gymnosperms and sudden appearance of angiosperms in great diversity in the Cretaceous Period of the Mesozoic
• origin of angiosperms is a mystery

Front 8

two ideas of why we see the sudden appearance of diverse angiosperms in fossil record: "early-risers"

Back 8

angiosperms actually arose earlier but have not been found in the fossil record

Front 9

two ideas of why we see the sudden appearance of diverse angiosperms in fossil record: "late-risers"

Back 9

fossil record is correct and angiosperms appeared and diversified in a very short period of time

Front 10

the angiosperm mystery is part of another controversy in evolutionary history: phyletic gradualism

Back 10

evolution proceeds at a constant, slow rate, requiring millions of years for speciation (Darwin)

Front 11

the angiosperm mystery is part of another controversy in evolutionary history: punctuated equilibrium

Back 11

evolution does not always proceed gradually, but is “punctuated” with periods of very rapid change and speciation (Stephen Jay Gould)

Front 12

_______ angiosperms preceded ________ angiosperms

Back 12

woody; herbaceous

Front 13

most primitive angiosperms

Back 13

angiosperms with numerous, leaf-like flower parts (e.g. magnolias)

Front 14

angiosperm evolution was paralleled by...

Back 14

insect evolution...many primitive trees are insect-pollinated (mags, tulip-poplar)

Front 15

in the present _________ era, ___________ are the dominant plants on earth, with incredible diversity

Back 15

Cenozoic; angiosperms

Front 16

why did angiosperm trees displace conifers in most of great forest areas of eastern U.S. except far north and far south?

Back 16

1. water transport
2. leaf morphology
3. reproduction
4. human influence
5. tolerance of seedlings

Front 17

why did angiosperm trees displace conifers in most of great forest areas of eastern U.S. except far north and far south?

water transport

Back 17

• conifers only have tracheids so they can move water great distances, but slowly 􏰂
• angiosperms have vessels that can move water more efficiently
  

Front 18

why did angiosperm trees displace conifers in most of great forest areas of eastern U.S. except far north and far south?

leaf morphology

Back 18

• most ang. leaves have more surface area than conifer needles, so they're more efficient at harvesting sunlight
• most ang. have deciduous leaves, so they conserve more water during winter compared with conifers that have leaves year-round
  

Front 19

why did angiosperm trees displace conifers in most of great forest areas of eastern U.S. except far north and far south?

reproduction

Back 19

• many hardwoods good at "cloning" (root suckering and stump sprouting), while most conifers are not
• hardwoods have faster sexual reproduction at rates 3-4 times higher than conifers
  

Front 20

why did angiosperm trees displace conifers in most of great forest areas of eastern U.S. except far north and far south?

human influence

Back 20

e.g. keeping fire out of longleaf pine region promotes hardwood invasion

Front 21

why did angiosperm trees displace conifers in most of great forest areas of eastern U.S. except far north and far south?

tolerance of seedlings

Back 21

hardwood seedlings more shade-tolerant than conifer seedlings so they can invade under the canopy and eventually replace conifers

Front 22

even more recent changes in our forests

Back 22

• exotic pathogens are wiping out trees
• exotic insect pests have become more invasive due to globalization
• invasive exotic plants
• global climate change: tree ranges are moving north as hardiness zones are changing, but this movement is poorly understood
  

Front 23

three ways to survey North American forest tree species

Back 23

1. taxonomic basis

2. forest region basis

3. mixed...what we will use

Front 24

Georgia includes parts of 4 North American forest regions

Back 24