FROM CHEMISTRY TO BIOLOGY

Transcription

1 Life on Earth

2 FROM CHEMISTRY TO BIOLOGY You re all atoms, in Earthly proportions. By number of atoms: H 55% O 28% C 10% N 5%

3 Water is Special Three-quarters of the Earth s surface is submerged in water The abundance of water is the main reason the Earth is habitable Figure 3.1

4 Overview: Carbon The Backbone of Biological Molecules All living organisms Carbon is Special Are made up of chemicals based mostly on the element carbon: organic chemistry Figure 4.1

5 The Formation of Bonds with Carbon The bonding versatility of carbon Allows it to form many diverse molecules, including carbon skeletons Name and Comments Molecular Formula Structural Formula Ball-and- Stick Model Space- Filling Model (a) Methane CH 4 H H C H H (b) Ethane C 2 H 6 H H H C C H H H Figure 4.3 A-C (c) Ethene (ethylene) C 2 H 4 H H H C C H

6 Molecular Diversity Arising from Carbon chains Carbon Form the skeletons of most organic molecules Vary in length and shape Figure 4.5 A-D H H H H H (a) Length H C C H H C C C H H H H H H Ethane Propane H H C H H H H H H H (b) Branching H C C C C H H C C C H H H H H H H H Butane 2-methylpropane (commonly called isobutane) H H H H H H H H (c) Double bonds H C C C C H H C C C C H H H H H 1-Butene 2-Butene H H H H C H (d) Rings C C H C H C C C C H C H C C Cyclohexane Benzene

7 Properties of Life Life is something that can reproduce and evolve through natural selection (a) Order (b) Evolutionary adaptation (c) Response to the environment (d) Regulation (e) Energy processing (f) Growth and development (g) Reproduction Figure 1.2

8 Photo by Peter Lik Take something as familiar as a tree

9 Photosynthesis Light + 6H 2 O + 6CO 2 C 6 H 12 O 6 + 6O 2

10 Photosynthesis light + 6H 2 O + 6CO 2 C 6 H 12 O 6 + 6O 2 light + water + carbon dioxide glucose + oxygen Plants take in water and carbon dioxide and rearrange the molecules into organic material like cellulose, respiring oxygen. In mass units: (water) (air) (plant) (air) Plants are 2/3 water but 90% of water is transpired so only 1 unit from water and 6 from air carbon is snatched from the air!

11 The cell A Closer Look at Cells Is the lowest level of organization that can perform all activities required for life Figure µm

12 All cells share certain characteristics They are all enclosed by a membrane They all use DNA as genetic information There are two main forms of cells Prokaryotic (lacks nucleus) Eukaryotic

13 DeoxyriboNucleicAcid The molecular structure of DNA Human DNA has 3 billion base pairs which accounts for it information-rich nature

14 The DNA double helix Consists of two anti-parallel nucleotide strands

15 Nucleic acids store and transmit hereditary information Genes Nucleic Acids Are the units of inheritance Program amino acid sequences Are made of nucleic acids There are two types of nucleic acids Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA)

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17 The Cell s Heritable Information Cells contain chromosomes made partly of DNA, the substance of genes Which program the cells production of proteins and transmit information from parents to offspring Nuclei containing DNA Sperm cell Figure 1.6 Egg cell Fertilized egg with DNA from both parents Embyro s cells with copies of inherited DNA Offspring with traits inherited from both parents

18 Unity in the Diversity of Life As diverse as life is There is evidence of remarkable unity 15 µm Cilia of Paramecium. The cilia of Paramecium propel the cell through pond water. 1.0 µm 5 µm Cross section of cilium, as viewed with an electron microscope Figure 1.16 Cilia of windpipe cells. The cells that line the human windpipe are equipped with cilia that help keep the lungs clean by moving a film of debris-trapping mucus upward.

19 The Origin of Species by Charles Darwin (1859) articulated two main points Descent with modification Natural selection Figure 1.18 Figure 1.19

20 Natural Selection Darwin proposed natural selection As the mechanism for evolutionary adaptation of populations to their environments Population of organisms Hereditary variations Overproduction and struggle for existence Differences in reproductive success Figure 1.20 Evolution of adaptations in the population

21 The products of natural selection Are often exquisite adaptations of organisms to special circumstances and the environment

22 The Tree of Life Darwin proposed that natural selection Could enable an ancestral species to split into two or more descendant species, resulting in a tree of life Large ground finch Geospiza magnirostris Seed eater Sharp-beaked ground finch Geospiza difficilis Large cactus ground finch Geospiza scandens Geospiza conirostris Cactus ground finch Cactus flower eater Medium ground finch Geospiza fortis Small ground finch Geospiza fuliginosa Cactospiza heliobates Seed eater Large tree finch Camarhynchus psitacula Woodpecker finch Cactospiza pallida Mangrove finch Medium tree finch Camarhynchus pauper Green warbler finch Certhidea olivacea Small tree finch Camarhynchus parvulus Vegetarian finch Gray warbler finch Certhidea fusca Platyspiza crassirostris Ground finches Insect eaters Tree finches Bud eater Warbler finches Figure 1.23 Common ancestor from South American mainland

23 Classifying life Species Genus Family Order Class Phylum Kingdom Domain Ursus americanus (American black bear) Ursus Ursidae Carnivora Mammalia Chordata Animalia Figure 1.14 Eukarya

24 The Modern Tree of Life Maps evolution via the gradual deviation of the base pair sequences in DNA or RNA Does not depend on identifying or recognizing distinct species Can track evolution back to the dawn of life but not with good time precision Places us as a minute twig on the tree of life

25 The Modern Tree of Life

26 Recognized Diversity of Life > 1,413,000 Species Higher Plants 248,400 Protozoa 30,800 Algae 26,900 Prokaryotes 4,800 Other Animals 281,000 Fungi 69,000 Insects 751,000

27 After four billion years of life on Earth, homo sapiens emerged to dominate the planet and venture into space. Was this just a fluke or did something like this happen anywhere else on distant planets?

28 Genetic Evidence for Human Evolution: Human Chromosome 2 23 Other primates have 24 pairs of chromosomes but Humans only have 23. How can we be genetically related? The answer: Human chromosome 2 is a fusion of 2 chromosomes from a common ancestor

29 Evolution is Convergent Eyes and brains and wings arose in different parts of the tree of life. Are bilateral body plans and central nervous systems inevitable?