Question
TOPIC 7.1 Introduction to Natural Selection
(a) – TOPIC 7.1 Introduction to Natural Selection
(b) – TOPIC 7.1 Introduction to Natural Selection
(c) – TOPIC 7.1 Introduction to Natural Selection
Fires frequently occur in some ecosystems and can destroy all above-ground vegetation. Many species of plants in these ecosystems respond to compounds in smoke that regulate seed germination after a major fire. Karrikins (KAR) and trimethylbutenolides (TMB) are water-soluble compounds found in smoke that are deposited in the soil as a result of a fire. KAR and TMB bind to receptor proteins in a seed. In a study on the effects of smoke on seeds, researchers recorded the timing and percent of seed germination in the presence of various combinations of KAR and TMB. The results are shown in Figure 1.
In a second investigation into the effect of available water on seed germination after a fire, researchers treated seeds with KAR or TMB. The treated seeds were then divided into two treatment groups. One group received a water rinse and the other group received no water rinse. The seeds were then incubated along with a group of control seeds that were not treated. The results are shown in the table.
(a) The researchers made the following claims about the effect of KAR and the effect of TMB on seed germination relative to the control treatment.
- KAR alone affects the timing of seed germination.
- KAR alone affects the percentage of seeds that germinate.
- TMB alone affects the timing of seed germination.
- TMB alone affects the percentage of seeds that germinate.
Provide support using data from Figure 1 for each of the researchers’ claims.
(b) Make a claim about the effect of rinsing on the binding of KAR to the receptor in the seed and about the effect of rinsing on the binding of TMB to the receptor in the seed. Identify the appropriate treatment groups and results from the table that, when compared with the controls, provide support for each claim.
(c) There is intense competition by plants to successfully colonize areas that have been recently cleared by a fire. Describe ONE advantage of KAR regulation and ONE advantage of TMB regulation to plants that live in an ecosystem with regular fires.
Answer/Explanation
Ans:
(a) The researchers made the following claims about the effect of KAR and the effect of TMB on seed germination relative to the control treatment.
- KAR alone affects the timing of seed germination.
- KAR alone affects the percentage of seeds that germinate.
- TMB alone affects the timing of seed germination.
- TMB alone affects the percentage of seeds that germinate.
Provide support using data from Figure 1 for each of the researchers’ claims. (4 points)
(b) Make a claim about the effect of rinsing on the binding of KAR to the receptor in the seed and about the effect of rinsing on the binding of TMB to the receptor in the seed. Identify the appropriate treatment groups and results from the table that, when compared with the controls, provide support for each claim. (4 points)
(c) There is intense competition by plants to successfully colonize areas that have been recently cleared by a fire. Describe ONE advantage of KAR regulation and ONE advantage of TMB regulation to plants that live in an ecosystem with regular fires. (2 points)
(a) KAR affects the timing of seed germination, as seeds germinate 12 hours sooner than the control group.
KAR also affects the percentage of seeds that germinate, as 20% more seeds germinate than the control group TMB affects germination time, as seeds germinate 3 hours later than the control group.
TMB affects the percentage of seeds that germinate, as over 60% fewer seeds germinate than the control group.
(b) Rinsing doesn’t affect the binding of KAR to receptors. Treatment groups 2 and 5 are both treatment with KAR, and, though treatment group 5 is rinsed, both behave differently than the control groups 1 and 4.
Rinsing does affect binding of TMB to receptor. Treatment groups 3 and 6 are treated with TMB. Treatment group 3 is unrinsed and be homes differently than control group 1. Group 6 is rinsed and behaves the same as control group 4. This shows that Rinsing causes seeds with TMB to behave the same as the control group. showing that rinsing affects TMB.
(c) One advantage of KAR regulation in pleats is that seeds germinate and begin to grow quickly after a wildfire, giving then first access to nutrients. One advantage of TMB regulation is that seeds grow again in the presence of water, so the seeds wait until a vital patient is present, in order for them to grow better, is present.