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