Download presentation
Presentation is loading. Please wait.
1
Phylogeny and Systematics
Ch. 25
2
Phylogeny Evolutionary history of a species or group of related species Reconstructing phylogeny is part of the scope of systematics Systematics—the study of biological diversity in an evolutionary context
3
Phylogenetic Trees Diagrams that trace evolutionary relationships as best as they can be determined Systematist use evidence from: Fossil record Phenotypic appearances Molecular biology Comparison of nucleic acid sequences/amino acid sequences DNA sequence analysis—identifying & comparing homologous sequences Species diverge as changes (genetic mutations) occur
5
Taxonomy Branch of biology concerned with naming and classifying the diverse forms of life Scientific name of an organism = binomial system Genus / species
6
Phylogenetic trees reflect the hierarchical classification
7
Cladistic Analysis Synonymous with phylogenetic systematics
Clade=evolutionary branch Classifying organisms according to the order in time that branches arose along a dichotomous tree Cladogram
9
Analyzing the taxonomic distribution of homologies enables us to identify the sequence in which derived characters evolved during vertebrate phylogeny. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
10
Kingdom: Plantae Plant Diversity
Ch. 29 & 30
11
Land plants evolved from green algae
Green algae called charophyceans are the closest relatives of land plants Four key traits in common: Rose-shaped complexes for cellulose synthesis Peroxisome enzymes Structure of flagellated sperm Formation of a phragmoplast Supported by genetic similarites in both their nuclear and chloroplast genes
12
Adaptations Enabling the Move to Land
In charophyceans a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out The accumulation of traits that facilitated survival on land may have opened the way to its colonization by plants
13
Land plants possess a set of derived terrestrial adaptations
Many adaptations emerged after land plants diverged from their charophycean relatives Five key traits appear in nearly all land plants but are absent in the charophyceans: Apical meristems Alternation of generations Walled spores produced in sporangia Multicellular gametangia Multicellular dependent embryos
14
Plant Characteristics
Multicellular eukaryotes Photosynthetic autotrophs Chloroplasts with photosynthetic pigments chlorophyll, carotenoids Cell walls contain cellulose Excess glucose stored as starch in plastids
15
Life Cycles of Plants: Alternation of Generations
Gametophyte—multicellular individual with haploid cells Produce haploid cells that fuse to form zygotes Sporophyte—multicellular individual with diploid cells Develop from the zygotes that are formed
16
Gametophyte Phase Dark round structures are antheridia or archegonia of the fern gametophyte (x12) The fern sporophyte grows from a fertilized egg in an archegonium on the gametophyte. (x12)
17
Sporophyte Phase Fern Fiddleheads Sori on Fern Leaf
Fern Leaf with Sori
18
Plant Phylogeny Origin of plants from aquatic ancestors— Ordovician period (475mya) Cuticle formation and jacketed gametangia Vascular tissue with conducting cells Diversification of seedless vascular plants—Devonian period (400mya)
19
Plant Phylogeny Origin of the seed—Devonian period (360mya)
Seed = plant embryo packaged with food store and protective coat Gymnosperms—early seed plants—naked seeds Emergence of flowering plants—Cretaceous period (130mya) Angiosperms—plants bear seeds inside flower’s protective ovaries
21
Classification of Plants I
Nonvascular Plants (Bryophytes) Division Bryophyta (mosses) Division Hepatophyta (liverwarts) Division Anthocerophyta (hornwarts) Characteristics: Small herbaceous plants (nonwoody) No vascular tissue, so relies on diffusion and capillary action to get water Need water to reproduce Gametophytes—larger and longer-living than sporophytes Sporophytes—typically present only part of the time Gametangia protect developing gametes antheridium—produce flagellated sperm archegonium—produce single egg
22
Division Bryophyta (mosses) Spongy mat—can absorb and retain water
Grips substratum with rhizoids (cellular filaments)
23
Bryophyta The green leafy structures are gametophytes.
The brown structures are sporophyte stalks and spore capsules.
24
Life Cycle of Moss
25
Division Hepatophyta (liverworts)
Division Hepatophyta (liverworts) Sporangia have coil-shaped cells that spring out and disperse spores LIVERWORT SPOROPHYTE
26
Division Anthocerophyta
Sporophytes are horn-shaped, elongated capsules that grow from the mat like gametophyte Photosynthetic cells have only one large chloroplast sporophyte gametophyte Division Anthocerophyta (hornworts) hornwort Phaeoceros
27
Classification of Plants
Vascular Plants Seedless Vascular Plants Division Lycophyta (lycophytes) Division Sphenophyta (horsetails) Division Pterophyta (ferns) Characteristics: Sporophytes are the larger generation Gametophytes are tiny plants that grow on or below the soil surface Terrestrial Adaptations: Roots-transport water Cellulose (structure support) Vascular tissue-xylem (water) and phloem (food) Pollen-eliminates need for water in reproduction Increased dominance of diploid sporophyte
28
Division Lycophyta (lycophytes)
Low-growing plants with rhizomes and true leaves Some are epiphytes (use another organism as a substratum Lycopodium annotinum Rhizome: stem like part of the plant from which the leaves grow Order Isoetales Quillworts
29
Division Sphenophyta (horsetails) sporangia
sporangia Division Sphenophyta (horsetails) Sphenophytes consist of only one genus, Equisetum, with about thirty living species known worldwide Homosporous-bisexual gametophyte produces egg and sperm
30
Division Pterophyta (ferns)
Most diverse seedless vascular plants Fronds-compound leaves Homosporous Sporangia borne on underside of specialized sporophylls Water necessary for fertilization Sporophyte develops within archegonium
32
3 Variations on Alternation of Generations in Plants
33
Evolution of Roots Roots are organs that anchor vascular plants
They enable vascular plants to absorb water and nutrients from the soil Roots may have evolved from subterranean stems
34
Evolution of Leaves Leaves are organs that increase the surface area of vascular plants, thereby capturing more solar energy that is used for photosynthesis Leaves are categorized by two types: Microphylls, leaves with a single vein Megaphylls, leaves with a highly branched vascular system According to one model of evolution, microphylls evolved first, as outgrowths of stems
35
Classification of Plants II
Vascular Plants Seed Plants Gymnosperms Division Coniferophyta (conifers) Division Cycadophyta (cycads) Division Ginkgophyta (ginkgo) Division Gnetophyta (Gnetae)
36
Seeds Replace Spores Relatively harsh terrestrial environment led to development of resistant structures for the dispersal of offspring Seeds more hardy because of multicellular nature Seed = sporophyte embryo + food supply surrounded by protective coat Seed plants are heterosporous Megasporangia produce megaspores female gametophyte Microsporangia produce microspores male gametophyte
37
Heterospory: The Rule Among Seed Plants
Seed plants evolved from plants with megasporangia, which produce megaspores that give rise to female gametophytes Seed plants evolved from plants with microsporangia, which produce microspores that give rise to male gametophytes cavehill.uwi.edu/FPAS/bcs/bl14apl/pter3.htm Micrograph of Selaginella
38
Ovules and Production of Eggs
An ovule consists of a megasporangium, megaspore, and one or more protective integuments Gymnosperm megaspores have one integument Angiosperm megaspores usually have two integuments
39
Pollen and Production of Sperm
Microspores develop into pollen grains, which contain the male gametophytes Pollination—transfer of pollen to the part of a seed plant containing the ovules Dispersal by air or animals If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule
40
The Evolutionary Advantage of Seeds
A seed develops from the whole ovule A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat commons.wikimedia.org/wiki/Image:Avocado_seed...
41
Division Coniferophyta (conifers)
Araucaria cunninghamii. The hoop pine. Lake Tinaroo Falls Dam, Queensland, Australia. Largest division of Gymnosperms -most are evergreens: pines, spruces, firs, larches, yews, junipers, cedars, cypresses, and redwoods
42
Yosemite National Park, Mariposa County, California.
Sequioadendron giganteum. The Giant Sequoia. Yosemite National Park, Mariposa County, California.
43
Division Coniferophyta (conifers)
Needle-shaped conifer leaves are adapted to dry conditions thick cuticle covers the leaf stomata are in pits, reducing water loss
44
Division Coniferophyta (conifers)
Mature ovulate cones and seeds
45
Heterosporous- both male and female gametophytes develop from different types of spores on separate cones
47
Division Coniferophyta (conifers)
Cedrus deodora. Near Placerville
48
Division Cycadophyta (cycads)
Living fossils—Jurassic Period is sometimes called the "Age of Cycads"
49
Division Cycadophyta (cycads) Cycas revoluta
50
Division Ginkgophyta (ginkgo)
Ginkgo biloba Division Ginkgophyta (ginkgo)
51
Division Gnetophyta (Gnetae) Ephedra andina. Mormon tea
Division Gnetophyta (Gnetae) Ephedra andina. Mormon tea
52
Classification of Plants II
Vascular Plants Seed Plants Angiosperms Division Anthophyta (flowering plants)
53
Reproductive adaptations of angiosperms include flowers and fruits
Angiosperms are flowering plants These seed plants have reproductive structures called flowers and fruits They are the most widespread and diverse of all plants
54
Division Anthophyta (flowering plants) Sunflower
California Poppy Sunflower Indian Paintbrush in Grand Canyon. Division Anthophyta (flowering plants)
56
Fruit develop from the ovary
57
Fruits A fruit typically consists of a mature ovary but can also include other flower parts Fruits protect seeds and aid in their dispersal Mature fruits can be either fleshy or dry
58
Fruits Various fruit adaptations help disperse seeds
Seeds can be carried by wind, water, or animals to new locations
59
The Angiosperm Life Cycle
In the angiosperm life cycle, double fertilization occurs when a pollen tube discharges two sperm into the female gametophyte within an ovule One sperm fertilizes the egg, while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm The endosperm nourishes the developing embryo
60
The Angiosperm Life Cycle
Similar presentations
© 2025 SlidePlayer.com Inc.
All rights reserved.