Question

• How does assortative mating explain why races still exist?
• How is skin color adaptive for different latitudes in terms of vitamin D and folate levels?
• TOPIC: PLANT BIODIVERSITY
• Name the 4 phyla of plants.
• Explain which produce spores, and which produce seeds.
• What is the significance of producing seeds rather than spores?
• Explain which have a vascular system and which do not.
• What the significance of having a vascular system as a plant?
  
  NO HAND WRITING PLEASE

Answer 1

• Assortive mating is the mating between individuals with similar phenotypic traits or characters.Assortive mating is also known as homogamy.Similar phenotypic traits include body size,skin colouration ,pigmentation etc.This mating increases the genetic similarity within a family.In assortative mating,mating of individuals with dissimilar phenotypes is rare.So this helps to maintain the races as matings will be within the race.
• Human skin colour is variable around the world.It is different for different region.The colour of skin is due to the pigment melanin.Melanin is produced by the cells located in the epidermis known as melanocytes.These cels have photosensitive receptors and detect he ultraviolet rays from the sun.In response to this ,they produce melanin.With the increase in UV rays ,more melanin is produced that result in various skin colur.People in northern latitudes have dark skin colour due to the abundant melanin production.Melanin protects our body from the harmful effects of UV rays (like sun burn,skin cancer ). Moreover folate (derived from folic acid) gets broken down in too much UV rays.Melanin preserves the folate from being broken down. Some amount of UV rays is required for the production of vit D.So people with dark complexion find difficult to live in northern latitudes as they cannot produce vit D . So people in different latitudes have different skin Colour in terms of vit D and folate levels.

PLANT BIODIVERSITY

• The four phyla of plants are :Bryophyta (mosses and liverworts),pteridophyta(ferns),gymnosperms (conifers)and angiosperms.(flowering plants)
  
• Significance of seeds than spores are:

1.seed coat protects the inside of the seed

2.seed contains endosperm that gives nourishment to the developing embryo.

3.seed contain fully developed embryo and and many seeds go through a dormancy period.So in right conditions only seeds germinate.having a developed embryo provides more chances of Survival than spores.

4.seeds donot need water.In dry conditions large seeds can hold water .while spores require water for germination.

• Non vascular plant phyla is the bryophyte that include mosses and liverworts.They donot have a root system.or stem.Leaves lose the water.Vascular plant phyla are pteridophyta,gymnosperms and angiosperms.
• Vascular system in plants is an association of conducting tissues and supportive fibres.Conducting tissues include xylem and phloem.Thgis helps in the easy transport of water,minerals to the leaves and food from leaves to all parts of the plant.