Class Notes (835,108)
United States (324,041)
BSCI 106 (116)
all (36)
Lecture

Lecture Notes Evolution of Plants

7 Pages
45 Views
Unlock Document

Department
Biological Sciences Program
Course
BSCI 106
Professor
All Professors
Semester
Fall

Description
Evolution of Plants 11/07/2012 Plant Origins Closest relatives are green algae Like land plants, chloroplasts have a double membrane and chlorophylls a and b, but relatively  few accessory pigments Cell walls primarily cellulose Starch as primary storage polysaccharide Life in water is easy Bathed in nutrients  Supported against gravity  Extensive transport not necessary  Gametes, offspring can be transmitted by water  No problem of desiccation  Land is a challenging environment Land plants must: Support their bodies  Avoid desiccation Photosynthesis evolved in water and machinery is still surrounded by water Transport water Transport nutrients 2  Evolution of Plants Transport gametes Why leave water? More light Enough ozone by 425mya to filter UV More CO 2 Diffuses more rapidly in air than in water More nutrients on land Initially No herbivores No competitors Themes in the Diversification of Green Plants Adaptations that allowed photosynthetic organisms to move from aquatic to terrestrial  environments Adaptations arose in two steps: prevention of water loss from cells transportation of water from tissues with access to water to tissues without access Preventing Water Loss Evolution of Plants 3 Cuticle Critical adaptation Cuticle is a waxy layer that prevents water loss from stems and leaves Tradeoff ­ cuticle also keeps necessary CO 2out of the plant Stomata Pore surrounded by specialized guard cells Stomata have pores that allow gas exchange in photosynthetic tissues The pore opens and closes as guard cells change shape Transporting Water: Vascular Tissue and Upright Growth The first land plants probably lacked rigidity and grew low to the ground  Vascular tissue allowed early plants to both support erect stems and transport water from roots to  aboveground tissues Most likely evolved gradually, providing increasing structural support, allowing plants to grow  more upright  Evolutionary Sequence Observed in Water – Conducting Cells Simple water­conducting cells Primary wall (with cellulose) Little structural support Found in fossils and present­day mosses Morphological Diversity: Nonvascular Plants 4  Evolution of Plants Nonvascular plants do not have vascular tissue to conduct water and provide support Evolutionary Sequence Observed in Water – Conducting Cells First vascular tissue Primary wall (with cellulose) Some structural support Found in fossils Lignin – a primary adaptation for upright growth found in cell walls of early water­conducting  cells A structural polymer built from six­carbon rings The defining feature of vascular tissues Morphological Diversity: Seedless Vascular Plants Seedless vascular plants have vascular tissue but do not make seeds Innovations that allowed plants to adapt to life on land How do plants reproduce in dry conditions? Sperm can swim to eggs 
More Less

Related notes for BSCI 106

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit