Lecture Schedule (middle third)
18 Feb KB – Fungi, Ch31
23 Feb KB – Prokaryotes & Protists, Ch28&29 Plant Diversity 25 Feb KB – Plant Diversity, Form, Function, Ch30&40 2 Mar KB – Plant Form and Function, Ch36&37 4 Mar KB – Plant Function, Ch38&39
9 Mar KB – Plant Ecology, Ch50,52,53 11 Mar KB – Ecology, Ch50,52,53 (Freeman Ch 30 & 40) 13-21 Mar Spring Break Videos 28-3, 28-5, 39-3 23 Mar KB – Biology of the Galapagos Wikelski 2000 and http://livinggalapagos.org/ 25 Mar KB - Part 2. Discussion and Review. 25 February 2010 ECOL 182R UofA 1 30 Mar KB - EXAM 2 2 K. E. Bonine
Figure 29-8 Plant Diversity
Bacteria Archaea Eukarya •From Sea to Land Chromalveolata Unikonta Discicristata Excavata Alveolata Stramenopila Rhizaria Plantae Opisthokonta Amoebozoa
s s te e ld y a s • Origins, Relationships, Diversity h te e o g a s p l a b m s e o a ll e e s t a e a i e e o s d id la x s a r n t e s g im l d a l s l le e g fe h y e a t a m l ia l n a e p t l i c h a g n l a s d o a a o s id g e s a n a p l la f ls r ri e a n s a m c i r lg a o e a o m e a m b e e fl o y m n m a o a n p i n a s l m e t h lo a l t o c o w a r c e d g a m o u s c c r g ia i m t o r o u d e n n o i b ll a m • Shared Derived Traits a r ip a u il in p o ia r o l la e r a u h n o e l li h B A D P E C D A O D B F C G R G L F C A L C P s (Synapomorphies) Green plants •Nonvascularto Vascular Plants •Seedlessto Seeds
Eight major lineages of eukaryotes (protist branches are in color)
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The Evolution of Land Plants Original Land Plants Related to Algae Land plants retain derived features they (from the edge of the swamp…) share with a green algae (Charales): • Chlorophyll a and b. •Starchas a storage product. • Cellulose in cell walls. Eukaryotic Green stuff
See Figure 30.9 5 6
1 Land Plants are Monophyletic Land Plants Comprise ~Ten Clades Nonvascular (3 clades) Land plants are monophyletic, all -paraphyletic group descendants from a single common ancestor. -liverworts, -hornworts Synapomorphy: development from an -mosses embryo protected by tissues of the parent plant. Therefore, also called Vascular plants, or tracheophytes embryophytes. (7 clades)—all have conducting cells called -tracheids. (phyton = plant) 7 -monophyletic group 8
Moving to Land Biological history Plants first appeared on land between 400–500 million years ago.
Environmental Challenges: 1. d 2. transport water to all parts 3. support (fight gravity) Plants first appeared on land between 400–500 4. disperse million years ago.
Some challenges met immediately, 9 10 others took millions of years
Biological history Adaptations for Land
Earth forms Origin of Life 1. Cuticle Oldest fossils -waxy covering thatretards water
Photo- synthesis 2. Gametangia enclosing gametes evolves
Eukary- Multi- 3. Embryos in a protective structure otic cellular cells
Abundant 4. Pigments that protect against UV life Moss radiation 5. Spore walls containing sporopollenin -resistsdesiccation and First land Forests Birds Aquatic life plants Insects Flowering First plants 6. Mutualistic relationships with fungus Abundant mammals Rise of fossils First land animals Dinosaurs Mammals First hominids - to promote nutrient uptake from soil dominant Homo 11 12 sapiens
2 Nonvascular Plants Are Plants Help Create Soil Similar to Ancestral Land Plants
Today’s nonvascular plants are Ancient plants contributed to soil thought to be similar to the formation. first land plants. Acids secreted by plants help break They grow in moist down rock. environments in dense mats Organic material from dead plants They are small, there is no contributes to soil structure. system to conduct water or Create habitat and pave way for minerals from soil to plant succession of other species. body parts. mosses 13 14
Extant Plants See Figure 30.9 Three Nonvascular Clades (paraphyletic group)
Liverworts
Hornworts Discuss ancestral first, Mosses then derived
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Alternation of Generations Moss Lifecycle (Nonvascular Plant) Water required Size and for egg and independence of sperm to meet gametophyte or sporophyte gametophyte, 1n changes
in sporangia
All plants have alternation of Sporophyte (2n) sporophyte, 2n dependent on, generations and attached to, (= multicellular See Figure haploid & multicelluar 30.17 See Figure diploid) 17 18 30.16
3 Nonvascular: Gametophyte Dominates Nonvascular Plant Reproduction
In nonvascular plants: Male: antheridium Female: archegonium gametophyte is larger, longer-lived, and more self-sufficient than the sporophyte.
gametophyte generation is
sporophyte may or may not be photosynthetic, but is always nutritionally dependent on the gametophyte, and is permanently attached.
Reduction of the gametophyte generation is a
major theme in plant evolution. 19 See Figure 20 30.17
Nonvascular Plant Life cycle of a moss Reproduction
Base of archegonium grows to protect embryo during early development.
Video 28-3 (land plants aka embryophytes) Mosses are sister group to vascular plants
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Harvesting Peat from a Bog Moss…
Sphagnum grows in swampy places. The upper layers of moss compress lower layers that are beginning to decompose, forming peat. Long ago, continued compression led to the formation of
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4 Paleozoic: Carboniferous • Large glaciers and swamp forests of treeferns and horsetails.
• Fossilized forests formed the coal we now mine for
Navajo Power Plant, Page, AZ 25 26
Vascular Plants Arose from Vascular Plants Comprise Seven Nonvascular Clades 10 clades of land plants:
Recently, fossilized fragments of ancient Nonvascular (3 clades) liverworts have been discovered. -liverworts, hornworts, and mosses -paraphyletic group
Vascular plants, or tracheophytes (7 clades) -conducting cells called tracheids. 27 -monophyletic group 28
Extant Plants Evolution of Vascular Plants
Vascular plants have a branching, independent sporophyte. Mature sporophyte is nutritionally Vascular, but independent from the Seedless gametophyte.
See Fig 30.12 Still must have water for part of the life cycle— for the flagellated, swimming sperm. 29 30
5 Figure 28.17 Horsetails Evolution of Leaves
Megaphylls:
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The Life Cycle of Mature gametophyte Life cycle of a fern (about 0.5 cm wide) a Homosporous Archegonium
Fern Egg Video Germinating Rhizoids 28-5 spore Antheridium Sperm Sporophyte and HAPLOID (n) Meiosis Fertilization Gametophyte are DIPLOID (2n)
each free-living Sporangium Embryo Microsorum sp. Sporophyte
Sori (clusters Mature sporophyte Roots Vascular but Seedless of sporangia) (typically 0.3–1 m tall) 33 34
Early Vascular Plants Bristlecone Pine During the Permian, the continents came together to form Pangaea. If you could imagine a living tree as old as the pyramids Extensive glaciation occurred late in of Egypt, what do you think it would look like? It would the Permian. look like a bristlecone pine, Pinus longaeva, the oldest known tree species in the world. Lycophyte–fern forests were replaced The bristlecone pine only lives in scattered, arid mountain by gymnosperms. regions of six western states of America, but the oldest are found in the Ancient Bristlecone Pine Forest in the White Mountains of California. There the pines exist in an exposed, windswept, harsh environment, free of competition from other plants and the ravages of insects and disease. The oldest bristlecones usually 35 36 grow at elevations of 10,000 to 11,000 feet.
6 Bristlecone Pine Which of the following are vascular plants? The oldest known tree is "Methuselah", which is 4,789 years old. To keep Methuselah from harm, this tree isn't labeled, as the other trees are. An older tree called Prometheus was killed shortly after it was a Juniper discovered in 1964. This happened when a geologist searching for evidence of Ice Age glaciers was taking b Sunflower some core samples from several bristlecones. Just as c Fern he realized he had found a tree over 4,000 years old, his coring tool broke. Amazingly the U.S. Forest d Moss Service gave him permission to cut down the tree. e Horsetail Prometheus turned out to be 4,950 years old. It was a 300 year old tree when the pyramids were being built f Liverwort in Egypt. g Lily Laboratory of Tree-Ring Research 37 38 http://www.ltrr.arizona.edu/
(Gymnosperms & Angiosperms) The Evolution of Seed Plants Seed Plants Late in the Devonian, some plants developed secondary growth: thickened woody stems of xylem. Small seeds Large seeds First species with secondary growth were the progymnosperms: seedless vascular plants, now extinct.
Wood: proliferated xylem, gives support and Penny allows plants to grow above their competitors
39 for sunlight. 40
Figure 29.1 Highlights in the History of Seed Plants Seed Plants Took Over
Surviving seed plants fall into two groups: • Gymnosperms: pines and cycads •Angiosperms: flowering plants
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7 Evolution of Plants Gymnosperms Horsetails and ferns (Pteridophytes) replaced by seed plants Extant gymnosperms are probably a clade. Gymnosperm: “naked-seeded”—the ovules and seeds are not protected by ovary or fruit tissue.
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Gymnosperms Living fossils: Gingko
Four major groups of living gymnosperms: • Cycads: Cycadophyta—140 species • Ginkgos: Ginkgophyta—one living species, Triassic Ginkgo biloba (~200mya) • Gnetophytes: Gnetophyta—90 species in 3 genera • Conifers: Coniferophyta—600 species, the cone bearers • Cycads and Ginkgos still have
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Cycas revoluta UA Campus gnetophyte Gingko biloba 47 Gymnosperms 48 http://arboretum.arizona.edu/plantwalks.html
8 Gymnosperm Evolution
Most living gymnosperms have only tracheids for water conduction and support. Angiosperms have vessel elements and fibers alongside of tracheids.
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Evolution of Seed Plants
Gametophyte generation is reduced even further than it is in ferns. Haploid gametophyte develops partly or entirely while attached to the sporophyte.
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Figure 29.3 The Relationship between Sporophyte and Gametophyte Has Evolved (Part 1) Figure 29.3 The Relationship between Sporophyte and Gametophyte Has Evolved (Part 2)
Nonvascular
Seedless Vascular Angiosperm
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9 Gymnosperm Evolution of Seed Plants Example:
Megasporangium Megasporangium is surrounded by (cone) integument made of sporophytic structures. Megasporangium and the integument Microsporangium together form the ovule (which (strobili) develops into a seed).
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Evolution of Seed Plants Conifers (Pine Cones…) In the microsporangium, A cone is a modified stem, bearing a tight microspores produce the cluster of scales (reduced branches), male gametophyte, or specialized for reproduction. Megaspores pollen grain with are produced here. sporopollenin in walls, the most resistant biological Strobilus: cone-like structure; scales are compound known. modified leaves. Microspores are produced here. Reproduction becomes independent of water in some Gymnosperms! Recall that evolution by natural selection How did this affect the evolution & typically involves modification of existing structures. diversification of seed plants? 57 58
Figure 29.8 The Life Cycle of a Pine Tree Pine Life Cycle
•Windcarries pollen grains from strobilus to cone. •Two sperm travel through pollen tube; one degenerates after fertilization.
Note that pollinization does NOT equal fertilization.
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10 Evolution of Seed Plants Evolution of Seed Plants
After fertilization, diploid zygote Seeds have tissues from three generations: divides to produce an embryonic 1. Seed coat develops from the sporophyte sporophyte. parent (integument). Growth is then suspended, the embryo 2. Female gametophytic tissue from the next enters a dormant stage, with the end generation contains a nutrient supply for product being a multicellular seed. developing embryo.
3. Embryo is the new sporophyte generation. How might suspension of growth be a fitness advantage? 61 62
Evolution of Seed Plants Evolution of Seed Plants
Seeds and Secondary Growth are the Seeds are well-protected resting stages. main reasons for the success of seed May remain viable for many years, plants—currently the dominant life germinating when conditions are favorable. forms in terrestrial environments. Seed coat protects from drying out as well as predators. Many seeds have adaptations for dispersal.
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Then came the FLOWERS! Origin of Land Plants
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11 Angiosperms Angiosperm Synapomorphies
•Xylemwith vessel elements and fibers Oldest angiosperm fossils are Cretaceous, •Phloemwith companion cells 140 million years old. • Double fertilization Radiation was explosive; angiosperms became • Triploid endosperm dominant in only 60 million years. • Ovules and seeds Over 250,000 species exist today.
Female gametophyte even more reduced—usually only
seven cells. 67 68
Small reproductive structures Large reproductive structures
Plant Female Male
Flower
Tip of sewing needle Perianth
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Figure 29.12 Carpels and Stamens Evolved from Leaflike Structures Carpels
Carpels Angiosperm: “enclosed seed”—the ovules and seeds are enclosed in a modified leaf called a carpel. Carpels provide protection, and may interact with pollen to prevent self- pollination. Stamens
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12 Flowers Flowers Stamens bear Petals (corolla) microsporangia: and sepals consist of (calyx) are filament and modified leaves. anther. Often play a Carpels bear role in megasporangia. attracting One or more pollinators. carpels form The calyx often (tepals) the pistil— protects the stigma, style, flower bud and ovary. 73 before it opens. 74
Flowers
Perfect flowers: have both mega-and microsporangia.
Imperfect flowers: either mega or microsporangia. Monoecious: “one-housed”; male and female flowers occur on the same plant. Dioecious: “two-housed”; male and female flowers on different plants.
75 76 www.bio.miami.edu/muchhala/home.html
Inflorescence: grouping of flowers. Different families have characteristic types.
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13 Angiosperm Double Fertilization (in Angiosperms) Lifecycle •One sperm nucleus unites with the egg nucleus to form the zygote. •Second sperm nucleus moves through the female gametophyte and fuses with the polar nuclei in the central cell to form a single triploid (3n) cell. • This triploid cell undergoes a series of mitotic divisions that form a triploid tissue called • Endosperm stores nutrients that will 79 be needed by the 80
Double Fertilization Produces a Inside the ovary, the ovule Zygote and an Endosperm Nucleus develops into a seed consisting of: • The developing embryo (2n) • The endosperm (3n), which provides nutrition to the growing embryo • Additional food storage tissue formed from the megagasporangium, called perisperm • Outermost layer of tissue, the integument, develops into the seed coat
The ovary itself develops into a fruit. • The ovary wall, aka pericarp, often
81 thickens & separates into distinct layers.82
The Angiosperms: Flowering Plants • Specialized leaves (petals and sepals) are important for attracting pollinators – Many angiosperms are animal-pollinated increasing the likelihood of outcrossing (in exchange for nectar or pollen) – Coevolution has resulted in some highly specific interactions, but most plant-pollinator systems are not highly specific
• Evolutionarily ancient angiosperms have a large and variable number of floral structures (petals, sepals, carpels, and stamens) – Evolutionary trend within the group: • reduction in number of floral organs, • differentiation of petals and sepals, • changes in symmetry, and 83 84 •fusion of parts.
14 Pollination Syndromes
• Beetle flowers: dull color, strong odor •Beeflowers: blue or yellow with nectar guides •Moth and butterflyflowers: long corolla tube •Birdflowers: lots of nectar, red, odorless •Batflowers: lots of nectar, dull colors, strong odors
85 •Wind: no nectar, dull colors, odorless 86
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Flowers pollinated by moths tend to bloom at night, are white, and are long and tubular.
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15 91 92
Wind pollinated angiosperms
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Angraecum sesquipedale Xanthopan morgani predicta
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16 Pollination by mammals!
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Video 39.3 Pollination of a Fruit & seed dispersal night-blooming cactus by a bat •Wind: fruits & seeds have “wings” •Water: fruits & seeds float •Animal(endozoochory): fleshy, edible fruits •Animal(exozoochory): bristles, hooks, or sticky substances
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17 Mistletoe berries stick to bird feet. Simple
Aggregate
Multiple
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Many seeds have bristles or hooks that stick to The Angiosperms: Flowering Plants animal fur. • Specialized leaves (petals and sepals) are important for attracting pollinators – Many angiosperms are animal-pollinated increasing the likelihood of outcrossing (in exchange for nectar or pollen) – Coevolution has resulted in some highly specific interactions, but most plant-pollinator systems are not highly specific
• Evolutionarily ancient angiosperms have a large and variable number of floral structures (petals, sepals, carpels, and stamens) – Evolutionary trend within the group: • reduction in number of floral organs, • differentiation of petals and sepals,
105 • changes in symmetry, and 106 •fusion of parts.
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18 Asteraceae
2 types of flowers
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Angiosperm Diversification Plants Support Our World More than 250,000 species
Plants contribute to ecosystem services: processes by which the environment maintains resources that benefit humans. Plants are primary producers: photosynthesis traps energy and carbon, making them available to consumers.
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Plants Support Us
Seed plants are our primary food source. Twelve are most important: rice, coconut, wheat, corn, potato, sweet potato, cassava, sugarcane, sugar beet, soybean, common bean, banana. Half of the world’s population gets most of its food energy from
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19 Plants Support Us
Many medicines come from seed plants. Medicines are found by screening large numbers of plants, or screening large numbers of chemical compounds. Ethnobotanists also discover medicinal plants by studying people and their uses of plants all over the world.
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