5.1a Communities, Ecosystems

29/04/2013 § Leave a comment

It’s the end of April, so close to May, and so close to the end of the year. This… is the last unit of HL Bio year one. I bring you – Ecology. We can start off with some key vocabulary that is apparently important but wasn’t mentioned in the reading. Weird.

  • a habitat is the environment in which a species normally lives
  • a species is a group of organisms that can interbreed and produce fertile offspring
  • a population is a group of organisms of the same species who live in the same area at the same time
  • a community is a group of populations living and interacting with each other in an area
  • an ecosystem is a community and its abiotic environment
  • ecology is the study of relationships between living organisms and between organisms and their environment

So, all animals need organic molecules in order to make their food, like glucose and amino acids (to make proteins, whooo). There are two kinds of organisms based on how they obtain their food sources. The autotrophs are self-feeders, so they make their own organic molecules out of inorganic substances, like plants. The heterotrophs eat other organisms. I think that says it all.

Organisms’ positions on the food chain are based according to how they get their food. There are also other ways for organisms to obtain organic matter from other organisms. The consumers ingest the actual organism and digest them. The detritivores ingest and digest the dead organism. The saprotrophs digest dead organic matter externally by secreting digestive enzymes onto the dead matter.

A food chain is what shows the order in which animals eat each other, basically. There are normally two to five organisms in the food chain. The organisms at the bottom are the producers, who are autotrophic because they get their food sources by making it out of inorganic matter. These include terrestrial green plant and phytoplankton – organisms that can do photosynthesis. Afterwards are primary, secondary, tertiary (and so on) consumers, who eat each other. These terms are called trophic levels, which is the organism’s level of consumption (?) in its food chain. Food chains and trophic relationships can also be illustrated by food webs, which are quite complex, look out.

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9.3b Plant Reproduction

15/04/2013 § 1 Comment

Okay, so this last bit is a continuation of how plants reproduce. How do they reproduce – it’s called flowering, pollination, and fertilization. Flowering gets really interesting later, not to mention confusing, but I’ll try to explain it as best as I can.

After a seed germinates, it grows a stem, roots and leaves and enters the vegetative phase. The plant can remain in the vegetative phase for as short as a few weeks up to as long as a many years. When meristems in the shoot start to produce the structure for flowers instead of leaves, then the plant has entered the reproductive phase. The flowers of plants produce pollen, which hold male gametes, and hold it out so that insects can find them easily to brush pollen they’re already carrying (they may or may not already be carrying pollen) to the stigma. This is called pollination, which is the transfer of pollen from an anther to a stigma. From there, the plant is fertilized when the pollen (holding the male gametes) travels down a tube on the stigma to the ovule, in order to fertilize the ovary. The ovary would then grow to be a seed of a fruit.

Quite important to learn is the job of the pigment phytochrome. This pigment has two forms – the dormant, inactive form Pr, and the active and energized form Pfr. When there is sunlight (so, during the day), Pr can absorb red light, which immediately converts it into the Pfr version. This means that during the day, all phytochromes are in their Pfr form. If Pfr meets strong, far-red light, it also immediately converts back to Pr. Rarely does this happen though, so Pfr normally converts back to Pr gradually and over night, when there is no sunlight to keep it in its Pfr form.

What phytochrome does is that it either inhibits or stimulates a plant’s ability to flower. Phytochrome binds to the receptor of the plant that controls its ability to flower, and whether it is in its Pr or Pfr mode, a particular plant will flower.

And now there are plants that are short day or long day plants. If a plant is a short day plant, it flowers during a short day. Short days and long nights are days during the Autumn or Winter, which means that this particular plant would flower when there is more Pr (because the long nights allow all the Pfr to convert back to Pr). Conversely, if a plant is a long day plant, which means days during the Spring or the summer when the night is the shortest, it flowers when there is more sunlight. This means that long day plants flower when there is a lot of Pfr (because the night is too short to allow all the Pfr to convert back to Pr).

I hope that made sense – that’s how I understand it.

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9.3a Plant Reproduction

13/04/2013 § Leave a comment

Up next on HL Biology, season 10 – Seed Structure & Germination, episode 4! In all seriousness, this is the second to last blog, also part one of the Plant Reproduction portion of the unit. Okay.

(Also, I hope everyone’s alright after that earthquake.)

This is a seed.

A seed is made up of an embryo root, embryo shoot, and cotyledon – either one or two depending on whether it’s a monocot or a dicot. The seed coat is called the testa and in it is a small hole called the micropyle. Seeds, though immobile, can travel long distances from their parent plant – called seed dispersal – and this is what helps spread the species around the environment.

In order for a seed to germinate (grow), they need need need water. Among the other things they need include oxygen in order to do respiration. Of course, plants know how to do anaerobic respiration, too, but remember that the addition of oxygen produces a much larger output than without oxygen. And another thing they need – warmth, which is what energizes the enzyme-catalyzed metabolic reactions. Temperatures that are too low fail to initiate germination but high temperatures – as we know – denatures enzymes therefore enzyme activity would be quite slow.

So, what happens during germination? WELL, LET ME TELL YOU.

  1. water is first absorbed and activates the cells metabolically
  2. gibberellin, a plant growth hormone, is produced in the cotyledons
  3. gibberellin stimulates amylase, the enzyme that turns starch into maltose
  4. the maltose is then moved from the food stores into the growth regions, which are the embryo root and shoot
  5. maltose is converted to glucose, used then for aerobic respiration or to make cellulose/other materials necessary for growth

And when the leaves have opened up, the plant can start photosynthesis to supply itself with food for further growth! Independent plants. Cool? Yeah, I’d say so.

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9.2b Plant Transport Systems

11/04/2013 § 1 Comment

Translocation in phloem

The phloem tissue inside plants is what transports sugars and amino acids. Phloem cells use energy to transport the substances, therefore the process is called active translocation. Areas where sugars and amino acids are loaded into the phloem are called sources, which include photosynthetic tissues like mature green leaves and green stems. Areas where the sugars and amino acids are unloaded and used are called sinks, which include growing roots and leaves or developing fruits and seeds.


Plants that live in dry areas, like deserts, are called xerophytes. These plants have numerous strategies to help them survive in these habitats, such as increasing the amount of water absorbed and reducing transpiration. Cacti are an example of a xerophyte, and they have leaves so reduced in size that they end up looking like little spikes. A cactus’s stomata would open at night, when the temperature is much cooler, therefore transpiration is a lot slower.

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9.2a Plant Transport Systems

09/04/2013 § Leave a comment

So, there’s a lot to cover for this blog, most of which has to do with transpiration and the root systems of plants.

Root systems and mineral ion absorption

The developing embryo is what makes the root of a plant. Once the embryo comes out of its seed, it continues to grow downwards into the soil, developing branches in some plants while other plants form complex networks of fibers and hairs. The point of these root systems is to anchor the plant in the soil, and absorb water and mineral ions with the increased surface area (via the hairs).

Water is absorbed through osmosis, so if the solute concentration inside the root is high, water will naturally move into the roots. The concentration gradients are established by active transport and can be up to 100+ times higher than the solution in the soil. That’s how water gets in. Mineral ions can only be absorbed through diffusion and the appropriate protein pump.

One other thing to note is that some plants absorb minerals and nutrients that benefit both it and a fungus that grows with it (?), and that would be a mutualistic relationship because both parties benefit.

Stomata and Transpiration

So we all know that one of the most important things plants need to live is water (what, really?!) and that an excessive loss of water leads to dehydration, a.k.a. death. Transpiration is the loss of water from the leaves and stems of plants. We’ve learned that the epidermis (the single outer layer of cells) has a “waxy cuticle” that reduces transpiration and prevents an excessive loss of water. However, for the plant to also absorb carbon dioxide (also necessary for survival, whaddup), there need to be breaks or pores in the epidermis and waxy coating – these are stomata! Of course, the problem with this is that though the plant can absorb the carbon dioxide, it could also lose some water in the process. « Read the rest of this entry »

9.1 Plant Structure

08/04/2013 § Leave a comment

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growth and the government (Chapter 15 Q & A)

03/04/2013 § Leave a comment

#1. 25 marks.

a) Outline three strategies which governments may use to increase their economic growth rates.

Economic growth is defined as an increase in the total output of goods and services (or GDP) in a nation over time. Rate would then be the amount of growth over time. Economic growth is one of the four macroeconomic objectives of nations. Governments can aim to increase their rate of economic growth by focusing on improving their productivity growth. This means that the government can improve their education, seek capital at the highest quantity and quality, and promote policies towards training their population. If the government can improve their population’s education, then they can raise smarter and more capable workers, therefore human capital would be improved upon through education. This means hiring better teachers, investing more in schools, and really spending more money on education as it is a vital factor in improving human capital. The government can improve their physical capital by increasing the quantity of capital per worker to increase their level of output, resulting in higher economic growth (because then all the workers would have more capital to work with, therefore they would all have the ability to produce more). The government should also invest in seeking the highest quality of capital, like replacing a farmer’s buffalo for an old tractor, and then later replacing that old tractor with a faster, more high tech version. This increases the productivity of that farmer, resulting in an increase of output of his goods. Finally, also to improve their human capital, a good government will promote policies that help to train and make better and more efficient workers out of the population. Not only will this improve a nation’s workers, it also provides jobs – for trainers, and would open up the R&D and HR departments for firms.

b) Discuss whether increasing the rate of economic growth should be the major policy objective of government.

In macroeconomics, a nation’s government doesn’t have only economic growth to worry about. They have three other objectives that they can focus on, and it always depends on their culture and history on what they value more. For example, Japan, between the four macroeconomic goals (low inflation, low unemployment, economic growth, and equal income distribution), would probably value low unemployment over economic growth because of their culture. Japan would break if too many people were unemployed, therefore increasing the rate of economic growth would not be a major policy objective of their government. The same can’t be said for the U.S. though, who seems to value economic growth as well as moving forward more than, say, low unemployment and equal income distribution. Improving and increase the rate of economic growth comes after many things, such as reducing unemployment, improving the quantity and quality of the nation’s resources, training and education the people to improve efficiency, and seeking better technology among other things. Economic growth should then be a long-term goal kept in the back of the government’s minds at all times, but should not be a hugely major policy objective.

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