bsci160 2

The Hadean

-4-5 billion years ago
-origin and early development of solar system and earth
-Reducing atmosphere of methane, ammonia, water, nitrogen, carbon dioxide, very little oxygen
-volcanoes
-meteor impacts
~3.7 bya - chemical origins of life

The Archean

-3.7 billion years ago
-the first living organisms
-unicellular prokaryotes (bacteria, archaea)
-anaerobic respiration

Characteristics of prokaryotes

-naked DNA
-small circular genome
-no membrane bound organelles
-few membranes
-no meiosis \= no sex
different flagella

Characteristics of eukaryotes

-linear double stranded DNA with histones \= chromosomes
-nuclear membrane
-membrane bound organelles
-endomembranes and filaments form a cytoskeleton
-mitochondria and, in some, chloroplasts
-sex, meiosis
-9+2 flagella

anaerobic respiration

Breaks down 6C (glucose) to 3C (pyruvate) (occurs in cytoplasm) - energy stored in the chemical bonds is released, used to ttach phosphate (P) onto adenosine di-phosphate (ADP) in a high energy bond --\> adenosine tri phosphate \= ATP

Glycolysis

the first step in the breakdown of glucose to extract energy for cellular metabolism. consists of an energy-requiring phase followed by an energy-releasing phase.

The Proterozoic

-2.7 billion years ago
-VERY LONG
-first photosynthetic organisms -cyanobacteria
-increasing O2 in atmosphere developed about 2.7 bya
-First oxygen revolution

consequences of the 1st oxygen revolution

-extinction of many anaerobes
-evolution of aerobic respiration
-protection from UV
-protection from meteor impacts
-evolution of eukaryotes ~2.2 bya
-evolution of mutlticellular eukaryotes ~1.7 bya
-evolution of advanced multicellular eukaryotes ~0.6-1.6 bya

Photosynthesis

six molecules of carbon dioxide (CO2) combine with 12 molecules of water (H2O) using light energy. The end result is the formation of a single carbohydrate molecule (C6H12O6, or glucose) along with six molecules each of breathable oxygen and water.

Late Proterozoic

\-570-540 mya
\-ediacaran fossil fauna

\-major animal groups diversified

\-fossilizing

Ediacaran fossil fauna

-animal fossils fairly rare prior to 570 mya
-there were very few simple organisms: cnidaria

Early/mid- Paleozoic

-The Cambrian Explosion
-2nd oxygen revolution
-scattered island continents around the equator
-two dominant benthic marine communities
-multicellular plants
-several mass extinctions

The Cambrian Explosion

almost all of the major animal phyla that we know today - and many that are not present today - appeared relatively suddenly between about 540 and 500 mya. Evidence suggests that it was just an explosion of fossilization because…


1. Burrowing bilateria
2. New fossil evidence of gastrula embryos
3. molecular evidence of divergence of bilateria

The 2nd oxygen revolution

\-due to proliferation of unicellular and multicellular algae in coastal waters, emergence of land plants in the Phanerozoic

\-protection on earths surface from space rocks

\-more protection from UV radiation

\-co-evolutionary adaptations bc of more respiration and emerging terrestrial animals

consequences of the 2nd oxygen revolution

-Protection from UV
-Protection from meteor impacts
-enhanced aerobic metabolism --\> greater body size and activity levels

Early part of Late Paleozoic

\-warm, wet
\-land plants, insects, amphibians, and early reptiles diversify

End of Paleozoic

-continents all congealing into Pangea
-shut down circum-equatorial current
-deterioration environment
-volcanism and/or meterorite
-GREATEST MASS EXTINCTION OF ALL RECORDED TIME

The Mesozoic

-slow recovery from mass extinction
-northern continents begin to separate from southern continents
-Americas begin to separate from Europe/Africa
-dominance by reptiles, molluscs, crustaceans in sea
dominance by reptiles and gymnosperms on land
-asteroid at Yuctan

2nd greatest mass extinction

\
* Meteor impact => mass extinction – Yucatan peninsula 
* Dust and firestorms over the northern hemisphere
* 75% of all species lost 

The Coenozoic

\-\~65 mya - present

\-Tertiary(65\~2.6 mya) (recovery from mass extinction, ancestors of homosapiens emerging, volcanic creation and rise of mountain ranges)

-Quaternary(2.6 mya -present) (increasing cold, holocene)

Tertiary era (Cenozoic)

\-65\~2.6 mya

\-Paleocene

\-Neogene

Paleogene (Cenozoic)

-Recovery- previously minor groups now become dominant
-warming, extensive reef development and diversification

Neogene (Cenozoic)

-Diversification in Miocene, but closure of Central American Isthmus in Pliocene\=shuts off circum-tropical current, deteriorating environment, extinctions

Quaternary Era (Cenozoic)

-2.6 mya -present
-rise of homo sapians
-pleistocene ice ages
-holocene/recent
-extinctions

"Background Extinctions"

normal extinctions that are going on all the time

"Mass Extinctions"

-atleast 9 (5 big ones)
-irreversible biotic upheavals that have occured repeatedly in earth's history
-play larger role than appreciated, remove dominant taxa and allow previously unimportant groups to diversify

Three "domains" of life

-Bacteria
-Eukarya
-Archaea: more closely related to bacteria than bacteria

Types of Bacteria

-Spirochaetes
-cyanobacteria
-chlamydiales
-actinobacteria
-firmicutes
-proteabacteria

Spirochaetes (bacteria)

ancient, basal group, many aquatic environments, many parasitic/cause disease, many groups anaerobic (syphilis, lyme disease)

Cyanobacteria (bacteria)

ancient, photosynthetic (1st oxygen revolution), marine

Chlamydiales (bacteria)

small group, parasites within cells, often anaerobic, sexually transmitted infections

Actinobacteria (bacteria)

DNA high in guanine and cytosine, produce many antibiotics (streptomycin, neomycin), cause tuberculosis, leprosy, plant roots, decomposers

Firmicutes (bacteria)

DNA high in guanine and cytosine, some fix nitrogen, many anaerobic, some photosynthetic. Cause anthrax, botulism, tetanus, boils, walking pneumonia, gangrene, strep throat.

Proteobacteria (bacteria)

all anaerobic, none photosynthetic. cause legionnaire's disease, cholera, food poinening, dysentry, gonorhea, diarrhea

Archaea

\-Crenarchaeota
\-Euryarcheota

\-inhabit extreme and regular marine environments

\-systematic groups

Crenarchaeota (archaea)

-oldest archaeans
-extremely hot, high pressure, cold, or acidic environments
-some of the most abundant organisms in ordinary marine environments
-more closely related to Eukaryota than are other archaea

Euryarchaeota (archaea)

-more derived groups of archaeans
-live in every conceivable type of habitat
-some are methane producing

Origin of Eukaryotes- two theories

1) autogenous theory
2) Endosymbiotic theory

Autogenous Theory

Some or all differences evolved gradually from the ancestral prokaryotes - perhaps the excavates

Endosymbiotic Theory

* Explains the origins of eukaryotic cells.
* Eukaryotic cells evolved from the symbiotic relationship between smaller prokaryotic cells
* The smaller cells were engulfed by larger cells but instead of being digested, they became mutualistic
* The smaller cells evolved into organelles, such as mitochondria and chloroplasts, while the larger cells evolved into the nucleus and other components of eukaryotic cells.
* The endosymbiotic theory is supported by…
* Similarities in the structure and function of mitochondria and chloroplasts to free-living bacteria
* Presence of DNA within these organelles that is distinct from the nuclear DNA of eukaryotic cells.

Endosymbiosis

-idea that mitochondria, chloroplasts were bacteria had been around before
-prokaryote ancestors of chloroplasts and mitochondria critical for development of photosynthesis and aerobic metabolism in almost all eukaryotes and in the evolution of multicellularity

Who was Margulis?

-1960's
-First convincingly and comprehensively developed the view that chloroplasts and mitochondria have prokaryotic origins
-national medal of science- 1999

Evidence for Endosymbiotic Theory

-Similar types of endosymbiosis elsewhere
-size of mitochondria/chloroplasts similar to prokaryotes
-similar membranes r in mitochondria/chloroplasts and prokaryotes
-mode of replication similar in mitochondria/chloroplasts and prokaryotes
-mitochondrial and chloroplast genome similar to prokaryotes
-similar transcription of DNA

Excavate Eukaryotes

-All anaerobic
-All unicellular
-2 groups:
Diplomonads
Parabasalids

Protists

-unicellular eukaryotes
-paraphyletic
-Three clades: Excavates, Photosynthetic, non-photosynthetic

Major components of the ocean's plankton

-Diatoms
-Dinoflagellates
-Silicoflagellates
-Cryptophytes
-Coccolithophorids
-Foraminiferans
-Radiolarians
-Ciliates

Diatoms (unicellular algae)

-Most planktonic, some benthic, attached to plants etc
-Colonial
~12,000 living species

Dinoflagellates (unicellular algae)

-mostly asexual reproduction
-most planktonic, some bethic
-sometimes form blooms, red tides, harmful algal blooms
-often leak toxins
-"Leakiness" gave rise to evolution of symbiotic "zooxanthellae" in corals and other invertebraes
-Bioluminescence

Coccolithophorids (unicellular algae)

\-Important vast blooms in North Atlantic and north pacific, fix carbon
\-Contribute to limestone and chalk beds
\-common at high latitudes

\-2 flagella buttons form “test”

Foraminifera

-CaCO3 chambered test - often colonial
-all marine, warm oceans

Radiolarians

-Delicate "test" of SiO2
-usually spherical with radiating spines

Ciliates

\-extremely diverse, some consider them and kingdom
\-macromucleus and micronucleus
\-cilia use locomotion and feeding
\-some have chloroplasts, some do not
\-common in fresh water

\-secrete or attach particles to form a test

Brown macro-algae, Red macro-algae, Green macro-algae

\-multicellular from protistan ancestors
\-all shown evolution of complex life

\-independently evolved

\-lack tissue and reproductive organs of land plants, fungi, and animals

Sporophyte

diploid- produces haploid spores by meiosis

Gametophyte

haploid- produces haploid gametes by mitosis

Advantages of Multicellular Algae Evolving

-exploit more than one food source during life cycle
-escape predators/parasites/competitors
-disperse to/colonize new habitats
-one phase can be sexual and the other asexual

Disadvantages of evolving

-highly hazardous, high mortality rate
-high reproductive cost
-may be difficult to find a mate for sexual reproduction in some phases
-may be difficult to find the different habitats for different phases of the life cycle

Non-photosynthetic eukaryotes

-Amoeboids/slime molds
-Xenophyophores
-Choanoflagellates

Amoeboids/slime molds (Non-photosynthetic eukaryotes)

\-asexual and sexual life cycles
\-saprobes

\-head end

\-terrestrial

\-directed “amoeboid” movements of cell aggregations

Xenophyophores (Non-photosynthetic eukaryotes)

-multinucleate cell syncytium
-amoeboid-like
-recently discovered in deep ocean trenches

Choanoflagellates (Non-photosynthetic eukaryotes)

\-solitary to colonial
\-cell structure like that in sponges = important link to animals

\-feeding current using flagellum and collar

8 Independent origins of multicellularity

1) unicellular to multicellular brown algae (kelp/sargassum)
2) unicellular to multicellular red algae
3) unicellular to multicellular green marine algae
4) unicellular green algae to multicellular fresh water algae and then to land plants
5) unicellular Amoebozoa to colonial/multicellular aggregates (slime molds and relatives)
6) Unicellular to multicellular fungi
7) unicellular Choanoflagellates to colonial/multicellular aggregates of Choanocytes
8) unicellular aggregations of different types of Choanocytes and Amoebocytes into animals (sponges and then Eumetazoa)

Why fossilizing in late Proterozoic?

1. Continental configuration
2. more oxygen
3. threshold increase in diversity

Origins of Land Plants

\-closest relative is green algae

\-→both unicellular ancestors

\-→chlorophyll b

\-→cellulose cell walls

What is the primary reserve material in green algae and land plants?

Starch

Examples of green algae

\-Chlamydomonas (unicellular, ancestral)

\-Volvox (multicellular, innovations)

Plants transition to living on land

through the evolution of Charales (containing stoneworts and pond weeds)

But life in water is easy :( (benefits)

\
* Bathed in nutrients
* Dense medium (supported against gravity)
* Gametes transmitted by water
* No problem of desiccation

But life in water can be hard too :(

\
* HUGEE competition during early paleozoic 
* Predation 

Life on land can suck (why)

\
* Must…
* conserve water
* transport nutrients
* withstand gravity
* transfer gametes
* protect or reduce vulnerable life stages
* Contend with herbivores eventually

Why leave water if land sucks so hard

\

1. More direct sun for photosynthesis
2. Enough ozone by \~ .5 bya to filter UV 
3. More concentrated nutrients and minerals on land


1. Roots!
4. Absence of predators at the start

Plants have 2 multicellular phases

\
* Haploid (gametophte)
* Diploid (sporophyte)

Haploid (gametophte)

\
Produces gametes

* By mitosis
* More conspicuous
* Photosynthetic
* Haploid 

Diploid (sporophyte)

Produces spores

* By meiosis
* Diploid

\
4 major successive radiations of land plants

Bryophytes

Pteridophytes

Gymnosperms

Angiosperms

Bryophytes (radiation of land plants)

\
* Mosses, liverworts, hornworts
* Dominant at beginning of phanerozoic 
* Can be abundant but in restricted habitats
* Limited by
* Lack of vascular tissues and support
* Reliance on water for reproduction
* Sporophyte & Gametophyte fairly similar in size, but...
* Gametophyte more conspicuous
* Only the Gametophyte is photosynthetic

Pteridophytes (radiation of land plants) 

* Vascular plants that do not produce seeds
* Reproduce via spores
* Have true roots, stems, and leaves
* Include ferns, horsetails, and clubmosses
* First plants to grow tall and form forests

Gymnosperms (radiation of land plants) 

* Vascular plants that produce seeds but do not have flowers or fruit
* Seeds are exposed on the surface of cones or similar structures
* Include conifers, cycads, and ginkgos
* Can survive in harsh, dry environments

Angiosperms (radiation of land plants) 

* Vascular plants that produce seeds and have flowers and fruit
* Flowers are used for pollination and fruit is used for seed dispersal
* Include the most diverse group of land plants
* Make up the majority of plant species on Earth

Green Algae (chloropyta)

\
* Includes charales 
* Stoneworts
* Pond weeds
* Land plants evolved from them 

Embryophytes

\
1\. Developed cuticle 

2\. Enclosed embryo root-like structures

3\. Root-like structures in gametophyte

4\. Vascular tissue

5\. True roots (vascular tissue)

6\. Seeds (naked)

7\. Very reduced gametophyte

8\. Flowers

9\. Fruit

Evolution of cuticle

Prevents water loss

Evolution of embryo root-like structures

Protects delicate embryo from water loss and predators 

Evolution of root-like structures in gametophyte

Attachment; absorption of water and nutrients

Evolution of vascular tissue

\
* Lignin
* Tracheophytes
* Ferns can grow really large and were the dominant large land plants of the late paleozoic

Lignin

organic polymer related to cellulose, hydro-phobic, strong, hard

Tracheophytes

Vascular plants

* Principal tracheophyte breakthrough
* This allowed
* Large size
* Efficient distribution of water

Why ferns could grow large in the late paleozoic

\
* Reduced, fragile gametophyte stages – subject to desiccation
* Sperm must swim for eggs
* Requires moist conditions
* Sporophyte is larger

Evolution of very reduced gametophyte

\-Can carry in the wind

\-protective seed coat

\-packed with food

\-carried by wind or animals

Evolution of flowers

\
* Animal mediated pollination
* Sepals and petals are modified leaves, not part of the flower
* All are part of the sporophyte

Evolution of fruit

Animal mediated dispersal

Evolution of fungi

\-most unicellular

\-most terrestrial

\-present in marine

\-symbiotic

\-protist (closest relative)

Fungi

more closely related to animals than plants

* molecular evidence (DNA/RNA)
* chitin
* independently multicellular
* \

Structure of Fungi

* Hyphae
* mycelium
* branching underground networks
* reproductive structure (mushrooms)

Hyphae

\-Thread like tubes in fungi

\-Chitin

Mycelium

many hyphae in mushrooms

Fungi life cycles

\
* 3 phases of life 
* 1. Haploid (1n)
* 2. Diploid (2n)
* 3. Heterokaryotic (n + n) – dominant multicellular stage in Fungi

Fungi asexual reproduction

\
* Mycelia produce spores via mitosis
* Diff from plants, they use spores via meiosis
* Spores develop into mycelia via mitosis

Fungi sexual reproduction

\
* Plasmogamy 
* Mycelia fuse cytoplasm creating a heterokaryotic mycelium with genetic heterogeneity
* Karyogamy
* Mycelia fuse their nuclei, forming a diploid zygote → mycelium

Fungi multicellular state

Mushroom

* A. heterokaryon
* B. some hyphae fuse nuclei → diploid basidium  = karyogamy 
* C. Then diploid basidium (2n) undergo meiosis to form haploid basidium (1n)
* D.  Haploid basidia (1n) undergo mitosis to form spores (1n)
* E.  Haploid spores (1n) germinate by mitosis, fuse cytoplasm \[=“plasmogamy”\]