General Ecology Lecture, Lecture notes of Wildlife Ecology

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ECOLOGY

(BIOL 311)

Lecture 1: Study of Life, The History of Life on Earth

Dr. Richard Whittington

Chapter 1 and 25

OVERVIEW: LOST WORLDS

 Past organisms were very different from

those now alive

 The fossil record shows macroevolutionary

changes over large time scales including

 The emergence of terrestrial vertebrates  The origin of photosynthesis  Long-term impacts of mass extinctions

Fig. 25-

NORTH AMERICA Chicxulub Yucatán^ crater Peninsula

 In each of the five mass

extinction events, more

than 50% of Earth’s species

became extinct

Fig 25-UN

Cryolophosaurus

MOLECULES OF LIFE

 All things are made up of the same units of

matter.

 Living things are made up of a certain subset of

molecules:

 Nucleic acids  Proteins  Carbohydrates  Lipids

http://images.google.com/imgres?imgurl=http://www.gifs.net/Animation11/Animals/Barn_Animals/Big_cow.gif&imgrefurl=http://www.animationlibrary.com/animation/29576/Big_cow/&h=214&w=300&sz=9&hl=en&start=6&tbnid=Qccnhz- Bdl0snM:&tbnh=83&tbnw=116&prev=/images%3Fq%3Deating%2Banimation%2Banimation%2Blibrary%26gbv%3D2%26svnum%3D10%26hl%3Den

ECOSYSTEM DYNAMICS

 The dynamics of an ecosystem include two major

processes:

 Cycling of nutrients, in which materials acquired by

plants eventually return to the soil

 The flow of energy from sunlight to producers to

consumers

SYNTHESIS OF ORGANIC COMPOUNDS

 Earth formed about 4.6 billion years ago,

along with the rest of the solar system

 Earth’s early atmosphere likely contained

water vapor and chemicals released by

volcanic eruptions (nitrogen, nitrogen oxides,

carbon dioxide, methane, ammonia,

hydrogen, hydrogen sulfide)

http://www.toysperiod.com/blog/lego/gold-rushes-a-playful-history/

POSSIBLE SEQUENCE membrane-bound proto-cells living cells

self-replicating system enclosed in a selectively permeable, protective lipid sphere

DNA RNA (^) other proteinsenzymes and

formation of protein-RNA systems, evolution of DNA

formation of lipid spheres

spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions

• Early protobionts with self-

replicating, catalytic RNA would have been more effective at using resources and would have increased in number through natural selection

• The early genetic material

might have formed an “RNA world”

Fig. 22-

Humerus

Radius

Ulna

Carpals

Metacarpals

Phalanges

Human Cat Whale Bat

MORPHOLOGICAL DIVERGENCE

o Change from body form of a common ancestor

o Produces homologous structures

Fig. 22-

Younger stratum with more recent fossils

Layers of deposited sediment

Older stratum with older fossils

THE CAMBRIAN EXPLOSION

 The Cambrian explosion refers to the

sudden appearance of fossils resembling

modern phyla in the Cambrian period (535 to

525 million years ago)

 The Cambrian explosion provides the first

evidence of predator-prey interactions

 By about 2.7 billion years ago, O 2 began

accumulating in the atmosphere and rusting

iron-rich terrestrial rocks

 The source of O 2 was likely bacteria similar

to modern cyanobacteria

 This “oxygen revolution” from 2.7 to 2.

billion years ago

 Posed a challenge for life  Provided opportunity to gain energy from light  Allowed organisms to exploit new ecosystems

PHOTOSYNTHESIS AND THE OXYGEN REVOLUTION

 The oldest fossils of eukaryotic cells date back 2.1 billion

years

 The hypothesis of endosymbiosis proposes that

mitochondria and plastids (chloroplasts and related

organelles) were formerly small prokaryotes living

within larger host cells

 Key evidence supporting an endosymbiotic origin of

mitochondria and plastids:

 Similarities in inner membrane structures and functions

 Division is similar in these organelles and some prokaryotes

 These organelles transcribe and translate their own DNA

 Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes

THE FIRST EUKARYOTES

Fig. 22-

Hawks and other birds

Ostriches

Crocodiles

Lizards and snakes

Amphibians

Mammals

Lungfishes

Tetrapod limbs

Amnion

Feathers

Homologous characteristic

Branch point (common ancestor)

Birds

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