The cycads, a mostly tropical phylum of gymnosperms, evolved about 300 million years ago and were dominant forms during the age of the dinosaurs. though their sperm are flagellated, their ovules are pollinated by beetles. these beetles get nutrition (they eat pollen) and shelter from the microsporophylls. upon visiting megasporophylls, the beetles transfer pollen to the exposed ovules. in cycads, pollen cones and seed cones are borne on different plants. cycads synthesize neurotoxins, especially in the seeds, that are effective against most animals, including humans.
which feature of cycads distinguishes them from most other gymnosperms?
1. they have exposed ovules.
2. they have flagellated sperm.
3. they are pollinated by animals.
1 only
2 only
3 only
2 & 3
1, 2 & 3

Over the past 60 years, many amphibian species have experienced significant population declines and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. chytridiomycosis is a fungal disease first identified in 1998 as a cause of massive amphibian deaths. in some severely impacted populations, a few individuals have survived, perhaps because of some natural resistance. if these resistant individuals continue to survive and prosper, new resistant populations might emerge. this would be an example of the founder effect artificial selection genetic drift natural selection sexual selection

Why is earth's outer core hotter than earth’s oceanic crust? earth’s oceanic crust is denser than earth’s outer core is. earth’s oceanic crust has lava flowing from the mantle. earth’s outer core has a composition of solid iron and nickel. earth’s outer core is deeper within earth than oceanic crust is.

Some scientists argue that global warming is related to buming fossil fuels to produce energy o increased use of fertilizers loss of forested areas a of the above