20.1 Origins of Plant Life TEKS 7A, 7E, 8C, 12A The student is expected to: 7A analyze and evaluate…

20.1 Origins of Plant Life TEKS 7A, 7E, 8C, 12A

The student is expected to:

7A analyze and evaluate how evidence of common ancestry among groups is provided by the fossil record, biogeography, andhomologies, including anatomical, molecular, and developmental;7E analyze and evaluate the relationship of natural selection to adaptation and to the development of diversity in and among species;


Continued:

8C compare characteristics of taxonomic groups, including archaea, bacteria, protists, fungi, plants, and animals; 12A interpret relationships, including predation, parasitism, commensalism, mutualism, and competition among organisms


KEY CONCEPT Plant life began in the water and became adapted to land.


Land plants evolved from green algae. • Plants and green algae have many common traits.

– both are photosynthetic eukaryotes – both have the same types of chlorophyll – both use starch as a storage product – both have cell walls with cellulose


• Genetic analysis points to the common ancestor of all plants.– extinct green algae species in class Charophyceae– modern charophyceans common in lakes and ponds


• Important plant characteristics likely originated in charophyceans.– multicellular body allowing for specialization of

cells and tissues

– cell division that allows for chemical communication between cells

– reproduction involving sperm swimming to egg


– Ancestral charophyceans lived in areas of shallow water.

• True plants evolved through natural selection.

– Those that could survive longer dry periods were favored.

– First true plants probably grew at edges of water.– True plants have embryos that develop while attached

to female parent.


• True plants evolved through natural selection.


Plants have adaptations that allow them to live on land. • Challenges of living on land have selected for certain

plant adaptations.• A cuticle allows plants to retain moisture.

– waxy, waterproof layer– holds moisture in


• Stomata are tiny holes in the cuticle.

stoma

– can open and close– allow air to move in and out


• A vascular system allows resources to move to different parts of the plant.

sugars

water and mineral nutrients

– collection of specialized tissues– brings water and mineral nutrients up from roots – disperses sugars from the leaves – allows plants to grow higher off the ground


• Lignin allows plants to grow upright.

– hardens cell walls of some vascular tissues– provides stiffness to stems

plant cells

lignin


• Pollen grains allow for reproduction without free-standing water. – pollen grains contain a cell

that divides to form sperm – pollen can be carried by

wind or animals to female structures


• A seed is a storage device for a plant embryo. – seed coats protect

embryos from drying wind and sunlight

– embryo develops when environment is favorable


Plants evolve with other organisms in their environment. • Plants and other organisms can share a mutualistic

relationship. – a mutualism is an interaction in which two species

benefit– plant roots and certain fungi and bacteria – flowering plants and their animal pollinators


• Plants have adaptations that prevent animals from eating them.

– defensive chemicals

– spines and thorns

Documents

20.1 Origins of Plant Life TEKS 7A, 7E, 8C, 12A The student is expected to: 7A analyze and evaluate…