Evolution of Angiosperms

3/19/2024 Evolution of Angiosperms Four Evolutionary Trends – – – – Few to many parts that are indefinite in number to few parts that are definite in number Floral axis shorten, floral parts often fused Ovary has become inferior rather than superior Radial symmetry has given way to bilateral symmetry Asteraceae – the family known for radial symmetry Orchidaceae – the family known for bilateral symmetry Double fertilization occurs in angiosperms – Produces a zygote (develops into embryo) and an endosperm (provides nutrition for the developing embryo) Pollinators – – – – – Bees o Can see UV nectar guides, but not red pigments (red appears black under UV light) § If a bee is on a red flower, it was probably led there by nectar guides o Good sense of smell o Consume nectar and pollen o Flowers normally pollinated by bees can sense when the bees are coming and produce more nectar & pollen in advance Butterflies o Require landing platform o Good color vision o Feed with proboscis Moths o Typically active at night o Good sense of smell o Also feed with proboscis o They occasionally hover o Flowers that bloom at night tend to be white/yellow (they can be seen at night) Birds (Hummingbirds) o Good color vision (they do prefer brighter colors) o Poor sense of smell o Need large amounts of nectar (birds eat a LOT) Bats o Active at night o o o o Colorblind Good sense of smell Need large amount of nectar Sturdy flowers (b/c these bats are big and heavy) Rodents, flies & beetles are also pollinators What happens when a pollinator goes extinct? – With no pollinator to fertilize it, the plant will eventually go extinct as well Flowers can also attract pollinators by resembling a mate for the pollinating animal Nectar robbers – pollinators who steal all the nectar and avoid carrying pollen to another flower (thus cheating the system) Fruits Parts of a Fruit – – – – – Exocarp: skin Endocarp: inner boundary around seed Mesocarp: tissue between exocarp and endocarp (the part that is usually eaten) Seed: hidden within the endocarp Pericarp: consists of endocarp, mesocarp & exocarp Simple Fruits (single ovary) – – Fleshy fruits: mesocarp at least partly fleshy at maturity o Drupe: single seed enclosed by hard stony endocarp o Pepo: relatively thick rind o True berry: thin skin and relatively soft pericarp o Hesperidium: leathery exocarp containing oils o Pome: Dry Fruits: mesocarp dry at maturity o Dehiscent fruits: split at maturity to release seeds § Follicle: splits along one side § Legume: splits along one side § Siliques & silicles: split along two sides, but the seed are on a central partition o Indehiscent fruits: do not split at maturity § Achene: base of seed attached to pericarp § Nut: entire pericarp very woody & hard § Grain: pericarp tightly united with seed § Samara: pericarp extends as wings for wind disperal § Schizocarp: twin-fruit that breaks into one-seeded segments called mericarps Strawberries are confusing!! – – The edible part of a strawberry actually develops from the receptacle of the flower The fruits are the tiny crunchy things in the flesh of the strawberry Compound Fruits (two or more ovaries) – – Aggregate fruits: derived from single flower with several pistils Multiple fruits: derived from several to many individual flowers in single inflorescence Seed Predators – – Seeds are high in protein and animals want to eat them Plants don’t want to be eaten, and their seeds that often contain secondary compound like cyanide (a poison) 3/21/2024 Human & Animal Dependence on Plants Spices vs. Herbs Herbs = leaves of plants Spices = bark, roots, stems of plants About 300,000 species of flowering plants – Only 6 of these species we need for food (provide 80% of consumed calories) o Wheat o Rice o Corn o Potato o Sweet potato o Cassava Fruits vs. Vegetables Cereals and Legumes Green Revolution (1950s) – Norman Borlaug