Sexual competition often occurs within complex social environments where male displays can be received by potential mates, rivals, or both at once. In brown-headed cowbirds’ breeding flocks, for example, multiple males sometimes vie directly for a single female’s attention; at other times males have opportunities to sing to females without interference. It was tested whether cowbirds vary the intensity of their signalling across contexts like these. The songs were recorded from males courting females both with and without a male competitor in sight. The recordings were now played to solitary, naïve females in sound attenuation chambers, and also to a naïve aviary-housed flock. The songs males had produced when they could see their competitors were more attractive, eliciting more copulatory postures from naïve females and more approaches from birds in the flock.
Scientists use fossils to learn about organisms' lives and evolutionary relationships, to understand geological change, and even to locate fossil fuel reserves.
Why does the amount or dose entering the body matter? ... A point would be reached where beneficial effects would disappear and harmful effects would start to be noticed. ... harmful is directly related to the amount of it taken into the body at one time. ... Chemicals with high toxicity only need small doses to cause poisoning.
The gynoecium of the flower(s) forms all or part of the fruit, which occurs from the maturation of one or more blooms. One or more ovules contain the egg cell of the megagametophyte, which is found inside the ovary/ovaries. These ovules will form seeds after double fertilisation.
