Chapter 28 and 29 Flashcards
Green algae
Paraphyletic group of photosynthetic organisms that have chloroplasts like land plants
Classified as protists, and living relatives of land plants
Examples: Mosses, hornworts, liverworts and all vascular plants
Why are green algae and land plants studied together
- Close relatives that form a monophyletic group
- Transition from aquatic to terrestrial life occurred when land plants evolved from green algae
Ecosystem
All organisms that live in a geographic area together with physical components of the environment such as atmosphere, precipitation, surface water, sunlight, soil and nutrients
Ecosystem services from green plants
Produce oxygen via oxygenic photosynthesis
Build soil by providing food for decomposers
Hold soil and prevent nutrients from being lost
Hold water in soil
Moderate climate by providing shade and reducing wind impact
Artificial selection
Deliberate manipulation by humans as in animal and plant breeding, of the genetic composition of a population by allowing only individuals with desirable traits to reproduce
How did biologists investigate green plants
- Morphological traits
- Fossil record
- Phylogenetic trees are estimated from similarities and differences in DNA sequences from homologous genes and whole genomes
Similarities between green algae and land plants
- Their chloroplasts contain the photosynthetic pigments chlorophyll a and b and the accessory pigment B-carotene
- Have similar arrangements of thylakoid
- Cell walls, sperm, and peroxisomes are similar in structure and composition
- Chloroplasts synthesize starch as a storage product
What green algal groups are the most similar to land plants
Zygnematophyceae (closest relatives to land plants)
Coleochaetophyceae
Charophyceae
Three categories of land plants
Nonvascular plants
Seedless vascular plants
Seed plants
Nonvascular plants
paraphyletic group of land plants that lack vascular tissue
Rely on spores for reproduction and dispersal
Ex. Mosses
Vascular tissue
Specialized cells that conduct water/nutrients throughout the plant
Seedless vascular plants
Have well developed vascular tissues but do not make seeds
Relies on spores for dispersal
Ex. Fern
Seed plants
Vascular tissue and produces seeds
Seed
Consists of an embryo and a strong of nutritive tissue surrounded by a tough protective layer and an outer protective layer (seed coat)
Gymnosperms
First seeded plants
vascular plant that makes seeds but does not produce flowers
Prominent from 299-145 mya
Grow best in drier habitats
Angiosperms
plants that produce flowers and bear their seeds in fruits
Appear 150 mya
Produce pollen grains transported via wind or insects
Five major intervals of fossil record of land plants
- Origin of land plants
- Silurian-Devonian explosion
- Carbon ferous period
- Diversification of gymnosperms
- Diversification of angiosperms
Cuticle
Watertight barrier that coats aboveground parts of today’s land plants and helps them resist drying
Why scientists believe fossils of the origin of land plants represent first land plants
- Possibly has an iteration of culpcile
- A material surrounds fossilized spores looks almost identical to sporopollenin
- Fossilized spores have been found in association with spore-producing structures called sporangia which is similar to sporangia in modern nonvascular plants
Sporopollenin
Waxy substance that encases spores and pollen of modern land plants and helps them resist drying
Sporangia
A spore-producing structure found in seed plants, some protists, and some fungi
Origin of land plants (first period)
Begins 475 mya
Spans 60 million yrs
Fossils dated from this period are fragments of plants and microscopic spores
Silurian-Devonian Explosion
The second major interval in the fossil records of land plants.
Fossils of major plant lineages are found in rocks dated 416-359 mya
During this period, plants colonized the land in conjunction with fungi. Fungi channeled nutrients from soils to plants, and plants produced sugars and other products of photosynthesis that were useful to bacteria in a mutually beneficial symbiosis
The carboniferous period
Third interval in fossil history of plants
Sediments date from 359-299 mya
Coal deposits is found in these sediments and since coal is formed with the presence of water, these carboniferous fossils indicate extensive forested swamps
The fossils derived from seedless vascular plants were ancestors of today’s club, mosses, horsetails, and ferns
Diversification of gymnosperms
The fourth interval in plant history is characterized by seed plants, gymnosperms
Fossil record from 299 mya to 145 mya
During this interval biologists infer wet and dry environments became blanketed with green plants as gymnosperms grow in dry habitats
Diversification of angiosperms
The fifth interval is happening now
Age of flowering plants, the angiosperms and are dated to appeared first 125 mya
Timeline of plants
According to the fossil record, green algae appeared first, then nonvascular plants, seedless vascular plants, and then seed plants
Resources that plants obtained from land after transitioning to dry land
Light: The large amount of light plant leaves recieved drove photosynthesis
Carbon dioxide: Another essential part of photosynthesis is plentiful above water
What adaptations did natural selection favor in land plants that allowed them to survive on land
- Preventing water loss, keeping cells from drying out and dying
- Providing protection from harmful UV radiation
- Moving water from tissues with direct access to water to tissues without direct access
Innovation that made transition to land possible
Random mutations lead to the production of cuticles.
As it is a waxy watertight sealant that covered the aboveground parts of plants and gives them the ability to survive in dry environments
How does the stoma help in photosynthesis
Helps CO2 diffuse into the interior of leaves and stems where cells are actively photosynthesizing
Guard cells
One of the specialized, crescent cells forming the border of a plant stoma
The guard cells change shape when they lose or gain water, when they lose water the pore closes and when they absorb water the pores are opened.
They allow CO2 in
Flavonoids
UV-absorbing compounds plants accumulate to protect themselves from UV light
Two problems from plants growing upright to obtain better access to sunlight than individuals that cannot.
- Land plants must transport water from tissues that are in contact with wet soil to tissues in contact with dry air against the force of gravity
- Land plants must be rigid enough to avoid falling over in response to gravity and wind
Lignin
Complex polymer built from six-carbon ring. Found in secondary cell walls of some plants
Why plants stay upright
The evolution of lignified vascular tissue allowed early plants to support upright stems in the face of wind and gravity and to transport water from roots to aboveground tissues
Tracheids
A long, thin, water-conducting cell that transport water and mineral salts through the Xylem of vascular plants
Secondary cell wall
The thickened inner layer of a cell wall formed by certain plant cells as they mature and after they have stopped growing; contains lignin in water-conducting cells. Provides support or protection
Primary cell wall
Outermost layer of a plant cell wall, made of cellulose fibers and gelatinous polysaccharides
Vessel elements
Short, wide, water-conducting cell in vascular cells that has gaps through the primary and secondary cell walls, that allows passage of water between adjacent cells
wood
Support material from tracheids or a combination of tracheids and vessels
Three innovations that occurred early in land plant evolution that was vital to reproduction in a dry environment
(1) spores were produced that resist drying
(2) gametes were produced in complex, multicellular structures; and
(3) the embryo was retained on the parent (mother) plant and was nourished by it.
Sporopollenin
Very durable polymer that surrounds that helps spores resist drying and survive for a long time
Gametangia
Organ where gametes are produced
Protected gametes from drying out or physical damage
Antheridium
Sperm-producing gametangium
Archegonium
egg-producing gametangium
Embryophytes
A plant that nourishes its embryos inside its own body
Alternation of generations
Plants alternate between two stages in their life cycle called the gametophyte and sporophyte stage
Gametophyte
Sexual phase in life cycles of plants and algae
develops sex organs that produce gametes, haploid sex cells? And participate in fertilization
Sporophyte
a diploid, multicellular spore-producing phase in the life cycle of the plant body which exhibits alternation of generations
Steps of alternation of generations
- The sporophyte produces spores by meiosis. Spores are haploid.
- Spores germinate and divide by mitosis to develop into multicellular, haploid gametophytes.
- Gametophytes produce gametes by mitosis. Both the gametophyte and the gametes are haploid, but gametophytes are multicellular while gametes are unicellular.
- Two gametes unite during fertilization to form a diploid zygote.
- The zygote divides by mitosis and develops into a multicellular, diploid sporophyte
Compare and contrast zygotes, spores, and gametes
- Zygotes and spores are both single cells that divide by mitosis to form a multicellular individual. Zygotes develop into sporophytes; spores develop into gametophytes.
- Zygotes are diploid, while spores and gametes are haploid.
- Zygotes result from the fusion of two haploid cells, such as a sperm and an egg, but spores are not formed by the fusion of gametes.
- Spores are produced by meiosis inside structures called sporangia; gametes are produced by mitosis inside gametangia.
Heterospory
It is the production of two distinct types of spores, microspores and megaspores
Homospory
The production of just one type of spore
Microsporangia
Spore producing structures that produce microspores that develop into male gametophytes, which produce sperm by mitosis
Megasporangia
Spore producing structures that produce megaspores, that develop into female gametophytes which produce eggs by mitosis
Fossil record of green algae and land plants
Green algae appear 700-725 mya
Land plants appear 475 mya
How plants have protection from UV irradiation
Make compounds that aborbs UV light such as flavonoids
Carotenoids protect plant against UV
Obstacles to reproduction when plants made transition from water to land
Gamete dispersal and lack of motility
Why spores (pollen) resist drying
They are incased in a tough coat of sporopollenin
How embryos are retained and nourished by parent plant
Land plants retain eggs inside the archegonia
Archegonia
Female reproductive structure in non-flowering plants such as mosses, ferns, hornworts, some algae and some conifers
Embryophyta
clade of plants that includes all plants producing an embryo and developing vascular tissue and comprises the embryophytes
Gametophyte dominant life cycle
In nonvascular plants (mosses) sporophyte is small, short-lived and dependent on gametophyte for nutrition
Sporophyte-dominant life cycle
In ferns and other vascular plants, sporophyte is much larger and longer lived than gametophyte
Sporophyte-dominated life cycle advantages
Diploid cells respond to varying environmental conditions more efficiently than haploid cells
What is microsporangia producing microspores mean
Develops into male gametophytes (produce sperm)
What does macrosporangia produce megaspores mean
Develop into female gametophytes
What kind of plants are heterosporous
Seed plants
Microsporangia –> microspores –> male gametophytes –> sperm
Megasporangia –> megaspores –> female gametophyte –> Eggs
Pollen grain
Tiny male gametophytes surrounded by a tough coat of sporopollenin
Evolution of this allowed plants living in dry habitats to reproduce
Seed
Include an embryo and store of nutrients provided by mother, surrounded by protective coat
Seeds allow the embryos to be dispersed to new habitats from the parent plant by wind, water or animals
Flowering plants (angiosperms)
Most diverse land plants living today
Two key reproductive structures of flowers (angiosperms)
stamens: produce the male gametes in pollen grains
carpels: contain the female gametes (the eggs inside the ovules),
Angio fertilization
Involves two sperm cells
One sperm fuses with egg to form diploid (2n) zygote
Second sperm fuses with two nuclei in female gametophyte to form triploid (3n) nutritive tissue called endosperm
Pollination
Transfer of pollen from stamen to carpel
Provides pollinators with food
Mutualism as the pollinator gets food and the plant gets fertilized
Fruit
Structure derived from ovary and encloses one or more seeds
Encourages seed dispersal by animals
Adaptive radiation
Single lineage produces large number of descendant species adapted to a wide variety of habitats
Parasites
absorb nutrients from and are harmful to their hosts
Mutualist fungi
Benefit the host plant by providing plant with water and key nutrients in exchange for sugars
Can help plants repel herbivores by producing toxins
Aids digestion of insects or serves as food for them
Negative impacts of fungi on humans
cause illness
Fungi cause fruit and vegetable spoilage
Positive impacts of fungi on humans
Source for many antibiotics, including penicillin
Mushrooms used as food
Yeast used to make bread, cheese, et cetera
Fungal enzymes used to improve characteristics of foods
Mycorrhizae
Association between fungi and plant roots allow for faster plant growth
Fungi’s effect on the carbon cycle
Accelerates it
Saprophytes
Fungi digests dead plant material such as cellulose and lignin (wood) to obtain organic compounds
Morphological traits of fungi
Single-celled forms (yeasts)
or
Multicellular filamentous forms
(mycelia)
Some species adopt both
Hyphae
Long, narrow, frequently branching filaments that make up mycelium
These filaments are thin enough to penetrate tiny fissures in soil and absorb nutrients inaccessible to plant roots
Separated into cells by crosswalls (septa)
Gaps in septa (pores) enable nutrients to flow between these compartments
4 types of reproductive structure of sexually reproducing fungi
Chytrids
Zygomycetes
Basidomycetes
Ascomycetes
Chytrids
Both sexually produced gametes and asexually produced spores in this group have flagella
Only known motile fungal cells
Zygomycetes
Have distinctive spore producing structures
Zygosporangia formed from fusion of cells from joined-together haploid hyphae from 2 individuals
Basidiomycetes
Form basidia: specialized club-like cells that form at the end of hyphae
Each basidium produces 4 spores
Ascomycetes
“sac fungi” form asci reproductive sac-like cells at the ends of hyphae
Each ascus produces 8 spores
Asci
sac-like cells where meiosis occurs and 8 spores form
What does fungi produce through asexual reproduction
Asexual spores called conidia
Key traits that links animals and fungi
DNA sequence data is more similar
Chitin synthesized by both animals and fungi
Flagella in chytrid spores and gametes are similar to animal flagella
Both animals and fungi store glucose as polysaccharide glycogen
Types of plant-mycorrhizal symbiosis
Ectomyccorrhial fungi
Arbuscular mycorrhizal fungi
Ectomycorrhizal fungi
is a symbiotic association of fungi with the feeder roots of higher plants in which both the partners are mutually benefited
Arbuscular mycorrhizal fungi
soil microorganisms able to form mutualistic symbiosis with most terrestrial plants
help in production of plant growth hormones, increase the nutrient availability and also inhibit the root pathogens.
Endophytes
fungi that live between and within plant cells
Increase drought tolerance of host plants
Produce compounds that deter herbivores
Receive benefits by absorbing sugars from plants
Lichens
complex life form that is a symbiotic partnership of two separate organisms, a fungus and an algae
Can be important as a food source and can initiate soil production in barren areas
Adaptations that make fungi effective decomposers
- Large surface area on mycelium enhances absorption
- Saprophytic fungi able to grow toward dead tissues that supply their food
Use extracellular digestion
