Kingdoms, Biodiversity, and Plant Reproduction
Kingdoms
Organisms are classified into kingdoms, which are subdivided into smaller and smaller groups. The last two groups are genus and species. These words give each species its scientific name.
Plants have green leaves, have cell walls made of cellulose, and can photosynthesize. This kingdom has four main groups:
- Flowering plants (reproduce using flowers)
- Conifers (reproduce using cones)
- Ferns (reproduce without flowers or cones)
- Mosses (no roots)
Main Groups in the Animal Kingdom
Some main groups in the animal kingdom are:
- Vertebrates (with backbones), which are divided into:
- Mammals (hair, have live young)
- Reptiles (dry scales, lay leathery eggs)
- Fish (slimy scales, lay jelly eggs)
- Amphibians (moist skin, lay jelly eggs)
- Birds (feathers, lay hard-shelled eggs)
- Invertebrates, including mollusks (fleshy pad to move) and arthropods (jointed limbs)
- Arthropods include insects (6 legs, 3-part body) and arachnids (8 legs, 2-part body).
Biodiversity
The range of species in an area is called biodiversity. We should preserve biodiversity because:
- Organisms depend on one another (they are interdependent).
- We won’t be able to make use of organisms if they become extinct.
- More biodiverse areas recover better from natural disasters.
Asexual Reproduction in Plants
Some plants can reproduce using asexual reproduction. This is when one parent plant is able to produce offspring (e.g., by using runners in strawberries or tubers in potatoes).
Sexual Reproduction in Plants
Reproduction produces new living things (offspring). Sexual reproduction needs two parents to produce sex cells, or gametes. The gametes fuse to produce a fertilized egg cell, or zygote. The zygote uses cell division to grow into an embryo, which can grow into an adult and become a parent (completing its life cycle).
The offspring from sexual reproduction contain characteristics from both parents. The differences in these characteristics is inherited variation. Gametes are produced by reproductive organs. In plants, these are contained inside flowers.
Pollination
The pollen grains made in the anther need to be carried to the stigma of another flower. Pollen can be carried by animals (such as insects).
Pollen can also be carried by the wind. The carrying of pollen from an anther to a stigma is called pollination.
Fertilization
Once on the stigma, a pollen grain grows a pollen tube, which enters the ovule containing an egg cell. The nucleus from the male gamete inside the pollen grain joins with the nucleus inside the egg cell to form a zygote. This is called fertilization. The zygote grows into an embryo, and the ovule becomes a seed, containing the embryo and a food store.
Seed Dispersal
A part of the flower forms a fruit. This is used for seed dispersal, which stops the new plants from competing with the parent plants for water, nutrients, light, and space.
- Some fruits are eaten by animals, and the seeds come out in their feces (e.g., apples).
- Some fruits are carried on the fur of animals (e.g., burdock).
- Some fruits are carried by the wind (e.g., dandelion).
- Some fruits explode, scattering the seeds (e.g., lupins).
Germination
When conditions are right, seeds germinate. The resources needed are water, oxygen, and warmth (WOW). Water allows chemical reactions to start, which break down the food store and allows cells in the embryo to swell up. Oxygen is needed for respiration, to release energy from the food store. Warmth is needed to speed up the chemical reactions.
The root grows first, then the shoot. Finally, new leaves open, and photosynthesis can start in the chloroplasts. The glucose from photosynthesis is turned into starch to be stored. The mass of material produced is biomass. Photosynthesis can be summarized as a word equation:
A growing plant needs light, air, water, warmth, and nutrients called mineral salts (LAWWN). The energy for growth comes from respiration, a process in which oxygen is used to release energy from glucose. It happens in the mitochondria of cells and can be summarized as:
Accuracy, Estimates, and Sampling
We can take a small sample of a larger population and use it to estimate what the larger population is like. Plant populations in an area can be estimated by taking samples using a quadrat. The more samples we take, the more accurate the estimate is likely to be, but the longer it will take to do.